This is the classic problem with all paradox games that I don't really have a solution for. Like as players we want them to support the game for a long time and keep updating it, but unless that's through dlcs then they can't really do that without getting paid somehow. The other alternatives are just not doing any updates and releasing a full new game every couple years which would probably have less features added compared to doing dlcs. Or having a subscription that you pay to get new updates which while I'm personally fine with I know a lot of people aren't. So that just leaves the current strategy of constantly doing dlcs and every once in a while releasing a new game and bringing over as many dlc features as they can to the new one while not making the development time unreasonable.
They could make games outside newer versions of the same game. Game studios used to (and many still do) make a game, put it out, then get started making a whole different game. Even with the modern ability to update games,
Put game out
Update game to deal with unforeseen bugs found once the masses have access
To be honest, I’d prefer for them to keep expanding a game I like. That’s what kept me playing SC1 for the past 65 years (or however long it has been since the game has been released).
But they point the comment above is making is that the years of support add a bunch of features that wouldn't exist otherwise. Sure, they could just not. Why would they do that though if they have a team who knows how to work on a thing and people willing to pay for it.
For example, BG3 exists because the studio continued to make games in the same style in the same engine for a very long time. They became absolute experts in it, and continuously improved their tools and techniques. You don't get that by constantly making new different games.
That's the FIFA, Madden model... release a game, fix a couple things, improve a thing here and there, pull a new roster in and voilà! This year's new sports game.
You're saying remake all the DLCs and not have people pay for it I assume. How the hell are they going to afford that? That's not mentioning they might not want to make identical DLCs, and many of the features from them are included in vanilla now.
When did I say that? I just let you know Paradox aren't the developers like you seem to think. They still need to keep the lights on though. Honestly, tiny indie devs can afford to do crazy things because there are a lot fewer people on the line who need to get paid. The larger the studio, the more careful they have to be. An indie game can run on passion alone.