High level playing can be interesting

Is a nat 20 not treated as a critical success? At least that’s how my 5e DM handles those.

DnD 5e does not have critical successes or failures on ability checks. Only attack rolls have critical successes and failures.
- Both 5e and the 2024 rules only crit / crit miss on attacks. But Baldur’s Gate 3 introduced them on checks, which muddied the waters.
  BG3 also did drinking potions as bonus actions, which 5e did not do but many DM’s (including those in several well-known real play shows) did as a house rule, then they incorporated it into the 2024 rules.
  What a mess.
- Well, I like the way my DM does it. I would say I’m surprised, but the logic behind the rules is way too far beyond my understanding and I regularly am thrown off by the exceptions.
Some DMs don't like critical success or failure on skill checks.
Those DMs are less fun.
Nat 20 adds one to the degree of success, which almost always means a crit unless you are dealing with something way above your level.
- How some crazies want ability checks to work:
  Player: I gesture vaguely towards the ancient dragon indicating I would like it to give me all of its gold and become my personal pet.
  DM: Roll a persuasion check
  Player: Let's see... Minus 4 because I'm still only level 2.... With a Nat-20 that's totals 16
  DM: Nat-20? By golly I guess that means you succeed - the ancient dragon and its entire hoard of treasure are yours now.
- That's Pathfinder rules, this is 5e
  formally there is no crit success in 5e

We played wtih a College of Eloquence bard for some high level play and he just couldn't fail some checks. He liked to roll and then get his 30 minimum.

Funnily enough it was treated as such, and same with the "critical miss"

With us it kind of depends on the situation. If a critical success or fail would make sense or be very funny we treat it as such.

One of the reasons I don't really like 1d20+stuff. Just as likely to get the best possible outcome as the worst.

ok so with 2d20 you're less likely to get the same number twice than with 1d20+5 and 1d20+15?
- Imagine you roll 3d6. There's exactly one way to roll a 3. You need all three of those dice to come up 1. But there are many ways to roll a ten. [{1,3,6}, {1,4,5}, {2,2,6} ...etc]. You're more likely to get totals in the middle of the range. If you rolled 3d6 many times and charted the outcomes, it would look like a bell curve. Most of the results are in the middle, with fewer results of the outliers like 3 and 18.
  If you roll 1d20 many times and chart the results, it's a flat line. You're just as likely to get one number as any other.
  Go play around with https://anydice.com/program/e6 if you like.
  I personally find the flat probability of 1d20 unsatisfying. I prefer when the average, most expected result comes up more often.
  Like imagine you're throwing darts at a dart board. You probably don't have an equal number of darts on the floor as in the bullseye, and also an equal amount in between. They're probably mostly clustered, with some outliers.