Speaking from personal experience, one reason minor nations get more attention than they should is that mod developers usually come in and work on nations they want to. Either because they have a personal interest in that tag, or it's a meme (see troono's Fiji tree). I never touched Red Flood again after they released with a broken unfinished USA tree, but a full tree for Prussian Congo. I'll give KRG this, at least they pushed out content for relatively important nations before anything else.
I strongly suspect for mods with bloated development teams, the only tags getting done in a realistic timeframe are mods. Even then, devs still have to write essays on DEEP LORE and justify every political path with a graduate thesis.
Paradox focus trees are trash, always have been, always will be. The mechanics were always of most interest to me, even if some of they really should be in the base game and some of them are just bloat. For Rises Again, I didn't even bother implementing MIOs and equipment designers for tanks and planes. The last thing TNO needs is more buttons to click