There’s no contradiction there. You are required specifically optimize your build for the difficult boss fights -and- play with Sekiro-like skill. The game is clearly designed like this. And while I’ve never played any of the previous AC games I agree with OP that this feels Souls-like, with stamina, poise and everything.
The combat is fine perhaps. The main reason I don’t like AC6 is because there’s nothing interesting in it except the boss fights. It’s the blandest FromSoft game I’ve ever played. Elden Ring kept me enthralled for a 100 hours until I got all achievements, trying to explore everything. An afternoon of AC6 I started to wonder why I was still playing, when after each mission or boss there’s just going to be more of the same.