I have been playing HOI4 for years and own a few core DLCs, but I never saw it as a problem. It will complicate things for the developers, but that is their problem, and as long as the game works for me, I am fine.My problem with the Paradox model is that it results in a very fragmented audience. They introduce core game mechanics and other important changes in DLCs. If you skip a pack, then you aren't just missing out on flavor for a small number of countries; you're missing out on important game mechanics. The next DLC can't rely on those game mechanics, though, because some players won't have them available. Keep doing that for a few years and you have a very complicated game with far too many different variants to support and a whole lot of DLC that doesn't interact with the rest of the DLC.
What I like in HOI4 is that devs are continuously developing the base game, and occasionally this means that older DLCs are rebalanced.