Counterpoint:
I find Stellaris, CK3, and Victorai 3 are fun to play.
By the numbers even New Paradox games are not fun. The market has spoken.
No one is arguing that no person in the world enjoys new Paradox. They are saying that they take away from the OG Paradox brand.
By... whose numbers? Steamcharts has CK3 consistently far above CK2 in terms of player count and that's probably the one modern Paradox game that really is just a worse experience all-around than its predecessor (with all DLC). Imperator failed, it's true, (though I think if it had *released* with its current systems, which are actually excellent for a map-painting game, things may have gone differently) but HoI4 is, at this point, just objectively better than HoI3. I still remember flamewars before launch over Paradox taking sliders out of EU4 and how it was clearly being dumbed down, now people complain about "bloat".
I encourage anyone who thinks Victoria 3 somehow represents a step backwards to actually sit down and play 8-10 hours of Victoria 2 HOD (vanilla, no HPM) instead of just comparing it to your rose-tinted memories. I won't go to bat for Victoria 3 and claim it's perfect or even excellent, but it's just obviously better than Vicky 2 no matter how you slice it. Trade routes, diplomatic plays, and production methods alone make it clearly just more complex than Vicky 2. You could argue about the simplification of combat but baiting the AI into fighting you in mountains with a tiny stack and then continually reinforcing the battle while you surround them with 1-stacks so you can wipe them is not, actually, better. I also won't miss manually optimizing stacks for the right number of engineers/artillery/hussars. If there's literally one strategy that is obviously optimal but following it is tedious, that's not "depth" or "complexity".
Compared to actually popular games/genres. League, Magic Arena, COD, Elden Ring, BotW, etc.
Or even 4X. Stellaris has 80% the players of Civ 5, and 30% the players of Civ6. And if you go out on the street and talk to random normies they will have no idea what Civ6 is.
As far as Vicky 2, I've been playing a wide variety of games from adjacent genres, actually doing Banished at the moment, so I played multiple dozens of hours of Vicky 2 about 3 weeks or so ago. No mods, well after the first half of the time I did some custom mods, just taking India away from the UK so can country could try and colonize the whole thing. Scramble for India is pretty fun. Of course there are downsides to Vicky 2. But the issue is Vicky 3 had 14 years of advancements on Clausewitz, plus advancements in game design and also graphics, and it is still worse than Vicky 2: HOD. Not by a landslide, but the problem is that it should be *better* by a significant margin since Paradox has a vastly superior engine, computers are much more powerful, and Paradox is a much larger company with piles of cash.
I feel the same way about CK3, though to be fair CK3 only had 9 years between the release and the release of CK2. CK2 was arguably substantially superior compared to Vicky2, though.
I don't have to compare Vicky 3 to anything but the potential of Vicky 3 itself, and by that measure it is a massive failure. Same for CK3. I was actually a fan of Imperator. The politics kinda sucked but the pop management, the military, and so forth had many strong points. I'd say the trade/building system was moderately worse than FoG:E but IMO pretty comparable to EU4. Trade goods were simple to some degree but they were majorly powerful in a way they aren't in EU4 outside a rare few examples. Actually the new EU4 merc system ruined my favorite trade good, Cloth.
The thing is that war is a "sidegrade" in Vicky 3, at best. Not an advancement. Diplomatic plays and maybe some of the manufacturing could be called a step up from Vicky 2 but not enough to carry the game.