The problem with Stellaris is conceptual
Look, there are no factories in game, all things get produced at a set pace, regardless of development, population or tech level. this goes from basic structures to starships (though there are starport modules that do, in fact, make shorter build times, they do not stack).
Planets are resource bases (either energy, mineral or research) and has a number of logic fails:
the star systems are empty, you might have some small resource bases off world, but they pale in comparison to planets (while it should be the opposite, the planets being industrial heartlands and the lifeless rock the strip mines)worse, some stars do not generate power to build an energy station... yet you can build a solar array module on a starport in that very star system and get a flat energy income
We could argue that lack of diplo options (for a pdx game) or that no logistics or range limitations are problems, those are true but side dressing.
The game at is core is crap, and nothing will fix that short of a serious overhaul.
But considering HOI4, PDX is going for mass market, dumbing down games to sell more.
A real shame, I used to respect this company a lot.