You don't get it. You currently need a guide or to spend hours to understnad what happens with all those DLCs. Imagine you don't know anything about the game. You open Steam page and you see you have to pay ~$200 for this game and all expansions. You saw screw it, it's clearly some sort of milking marketing gone mad. You don't know half of those money are spend on irrelevant and purely cosmetic stuff and basic version is still supported and updated. You see wall of DLCs.
To even consider buying a game like this you have to be bombarded by explanations how it works. It's lose-lose. Even after you know about every single DLC you have to scroll all of them and carefuly select the ones you want. Why won't someone in Paradox spends 10 minutes to organize this stuff into packs? I can't imagine. Maybe hope that someone says "screw it" and just buys everything. Well I'm sure much more people would prefer not to spend time on a game requiring you to read manuals to just buy it.
This is actually true.
I've spent about 800 hours in this game and own every major DLC plus many minor ones, yet I'm not even sure if I would be able to name just the major DLCs without forgetting anything or looking them up.
I know from experience with other games that it can become quite frightening to come to a Steam store page, seeing some base game for 10 bucks with 50 pieces of DLC for a huge amount of money.
I have read in this forum (I think Johann wrote it) that PDS won't release any 'Complete' editions anymore, since they want to keep the possibility to further extend their games with new DLC.
Nonetheless, clarity of what DLCs exist should really be improved. If you google 'Eu4 DLC', you only come up with a wiki page (that "may need to be updated", so you don't even know if it's accurate) and really have to collect all that information by yourself piece for piece.
That being said, I'm happy that PDS is trying their best not to split the community and providing everyone with most of the new features on any patch - while you're playing a different game when you play with or without DLC, it's no completely different one.