Don't know what to say here.
Number trumps design, but against an equally strong opponent design does make a difference. Its also possible to win outnumbered if you optimize towards the enemies weaknesses and the enemy allows this to happen (AI). There also is room for micromanaging, mostly on the galaxy map but on the star map as well, more so in the early game than in the late game were millions of fleet power smash into each other and you manically laugh as you consign a billion lives to oblivion.
Having a technological advantage is super important, especially if you are the underdog, because more advanced offensive and defensive technology makes a noteable difference. But since any form of wealth in Stellaris springs forth from pops, forget about playing tall. More planets = more pops = more tech = more boom.
Quick detour, I think that the fact that pop growth has negligible negative consequences and is the singular most important resource is one of the remaining weaknesses of the game. There is zero reason not to maximize pop growth at all times and design your empire towards that goal. What I would like to see is the pop growth civics changed to give bonuses to
maximum (possible) pop growth and that pop growth is dynamic according to how well you are able to satisfy the needs (food, consumer goods, stability, amenities, happiness) of your population. This would be more realistic, raise player skill and allow for more diverse empire configurations.
The hyperlane rework is one of the best things to happen to t2.his game, as you now have an actual map with strategic properties to paint on. I very much like how the map becomes more dynamic semi-organically over the course of the game with progressing tech. This gives the entire galaxy some sort of cohesion, like you're all sitting in the same boat, something that was obviously inspired by Victoria 2.
Of course, aggressively projecting your power in the galaxy by fleets is better than playing defensive. But it is certainly possible to play defensive, with the new additions to the game like planetary rings you can turtle up pretty good.
Overall I find the combat very satisfying, it feels like the outcome of the battlefield is the outcome of your grip on your empire, as it should be.