This is a very concise and very accurate assessment of the state of war in the game right now. Thank you for putting it in clearer English than I can manage at the moment!
Indeed. Stellaris either needs to at bare minimum, pick whether it wants many little wars (ala CK2) or few big wars (ala EUIV), instead of the terrible combination of the worst of both. If it wants the former, it needs to make the wars much faster (and/or blitzable) like CK2, where once you;ve occupied the "duchy" (i.e. the 2-3 worlds you're allowed to swipe), you get your 90-100%, bang done. If it wants to do the big wars, it needs to be like EUIV with flexible war goals and adjusting the warscore so you can gobble up whole small-to-mid sized nations or do all sorts of fun stuff.
I think part of the problem seems to be PDX are implementing all the anti-blobbing features they've been steadily adding to CK2 and EUIV, except at the moment, Stellaris doesn't have anything LIKE the depth of those games granted by the numerous expansions to leven that.
At the moment, it's an absolute archeyptal 4X, not a grand strat and it needs, as Mezmorki says, to pick which one it wants to be. If it want to be a 4X, it needs to admit it and seriously polish up the combat, because it needs to be able to compete with the gold standard that is SotS (and it ain't there yet). If it wants to be a grand strat, it needs to pick which grand start style, make diplomacy MUCH more engaging* and, for a kick-off, totally change the starting boundary conditions from practically-but-not-quite archetypical 4X to something closer to a randomly generated "New World" EU style. It's part-way there, but not part-way enough and needs to be so give us a decent Space Politics, especially since it doesn't (like Ck2 or EUIV) have an "end-point." (Come to that victory conditions would need to be SERIOUSLY changed, maybe even adding "beat end-game crisis" as one of them. I know I just gave up after that on my last game, since conquering the rest of the galaxy (and the 90-odd worlds I needed to do) was just going to be tens of hours of tedium of taking 3-4 worlds at a time, with the outcome never in doubt.)
If it wants to do both, which is a much harder job, it needs to pick which one it wants to do
first, because it also is very unlikely to be able to work both ends satisfactorally at once.
*Seriously, I find the current diplomacy system utterly indistingiushable from any other 4X or Civ diplomacy.