Imagine everything humans could accomplish if we were not a commerce based civilization.

Capitalism may hold us back in some regards but really helps in others.

The majority of people would likely be feudal peasants, working under a warmonger family that owns the sustaining land by force. No upward mobility except through bloodshed.

I suppose not much has changed then
The majority of people ~~would likely be~~ are feudal peasants, working under a warmonger family that owns the sustaining land by force. No upward mobility except through bloodshed.
FTFY
- No you don’t understand, this 9-to-5 job that’s slowly but surely wearing me down is just a stepping stone to my millions of $$. That’s why I keep voting for tax breaks for the rich; because I’ve just been temporarily down on my luck for 30 years. /s
- No, if you're lucky, clever enough, overwork yourself, or manipulate others you can live a somewhat comfortable life. Those methods don't require taking a life.
Capitalism optimizes for efficiency. Sadly slavery is terribly efficient in terms of economics. Therefore capitalism needs to be capped by society at certain acceptable limits. Which is called socioeconomics and its not perfect but the best system we have. insert handwavy remark about whatever america is doing here
Thats still in a sense a commerce based system. The only reason that warlord fights for that land is because it has value, be it food, a cash crop, a strategic location.
Warlords hoarded land and power in similar ways billionaires hoard money and power.
That's literally how it is now
Capitalism optimises for concentrating resources.
Dividends, return on investment, profits, etc. are all inefficiencies in the production of value, and require more resources, labor, and suffering per unit of value than for example a circular economy.
But it does concentrate wealth efficiently, which in turn gives access to enough resources to start larger ventures.

Commerce is just the exchange of goods and services. If we all stop exchanging goods, in what sense would we have a civilization? What would you or anyone accomplish if you had to grow your own food, make your own clothes, build your own house...?

Commerce is fine, greed is not. OP missed that distinction.
- Commerce != currency
An exchange of goods and services means you get nothing unless I get something. Maybe OP means everything is given as you take what you need with nothing expected in return.
You grow carrots, you bring them to town once a week. Other lady raises chickens, brings eggs once a week. If you need either you take some. You use the eggs to make cookies, you have extra, you give them away to anyone you see for the day.
- This works at a feudal technology level. Who makes the trains? They train makers need steel and literally no one would work in a forge or a mine for fun/preference.
  Who makes computer chips?
A lot more than we do in this shithole

I kinda feel like we would have done way, way worse without commerce. We're social beings. We do better when cooperating than trying to go at it alone. Commerce is merely one of the many glues that keep us cooperating on some level. Yes, it also leads to competition; but less so than it would without it. Why kill you and take what you have that I want when I can just give you something I have that you want for it?

Capitalism, and making commerce the end all be all of civilization is what we could do without. It's a means to an end, not the goal.

Interesting, what would be the alternative? Technology, culture, religion, military? Taking those options out of Civ

I think that's the key question. Like, I get capitalism is hedgemonical (is that even a word?), but what alternative do you propose?
- "Capitalism is the worst economic system, except for all the others."
- You could start by giving everyone a share of profits rather than pushing all the money up towards the people who have the most.
  Let machines do the work so we can do what we want with our time. We're working more than people did in the past despite our technology. And the reason we have to is the alternative is starving to death in the streets.
  Both of these things violate the principles of capitalism.
- Kinda the spelling is hegemonic for further reference.
- Not having merit based on how much money something makes would be a start.
- barter system worked fine for thousands of years
religion
I'd love to see how that one plays out. Lol
- Tbf we ostensibly already have and are again.
Being a lonely hunter gatherer.
If you have crafted nice spears and axes, but you have no food, that’s too bad. You’re not allowed to barter with talented hunters who can’t make spears as nice as you can. Go hunt your own food or die of starvation in this non-commerce based society.
Oh wait, how about we allow trading after all?
- Comparative Advanta-whoosy whatsits?
  Seems complicated, let's get rid of it.

I'm currently reading The Day The World Stops Shopping by JB Mackinnon, which argues the same point you're asking about, I think you'd find it interesting.

https://www.jbmackinnon.com/the-day-the-world-stops-shopping

imagine everything humans could accomplish if we used billionaires as food and fuel

Wouldn't using them as food just be using them as fuel anyways? The only difference is what you're going to fuel with them.
- came to say this. food is fuel, we are merely labyrinthine biological furnaces that chemically incinerates whatever unfortunate matter may enter us. the fuel's affluence is not typically relevant, but I'm a little out of touch on the science, I might be wrong.

If you feel the need to defend capitalism, then you should read "The Jungle".

What is a commerce based civilization? Isn't everything commerce based?

Wow. Good luck building your stick cabin in the woods all by yourself and growing and foraging all your food because you refuse to trade your labor for produce from a farmer because that would be evil commerce.

Project much? 🤣🤣🤣
- Your title is literally putting down commerce and you accuse me of projection? I don't think you know what projection means.
  You probably don't even know what commerce means.

Well, we would be still in caves cause commerce is the basement of civilization

Is it time to advance to the Fortress Age?

What about a meritocracy based system where any type of contribution is rewarded, whether it be research, garbage cleanup, etc.? (I’m sure there’s holes to poke in it, just thinking outside of the box.)

The problem with that and most other proposals for whatever other moneyless utopian society is that they all implicitly require some manner of all-powerful central authority to ensure that the rewards get distributed, the labor gets allocated, and the rules stay followed.
And we already know how well that's going to turn out.
- True meritocracy also leaves the disabled, elderly, or otherwise unable to contribute in the cold.
- And yet here you are, in the fediverse.
- he problem with that and most other proposals for whatever other moneyless utopian society is that they all implicitly require some manner of all-powerful central authority to ensure that the rewards get distributed, the labor gets allocated, and the rules stay followed.
  that really isn't the case..
  Communism by definition is not only moneyless but also stateless and classless (if there is an "all powerful" anything - it isn't communism).
  anarchism by definition abolishes all hierarchy, so again, no one person or even group gets to a point of having any significant power over anyone else.
  In both cases (which are the two most notable far left ideologies I would say, along with socialism which is inherent to both) not having an all powerful central authority is literally the point.