One author that gets short shrift but who is one of the best is Jack Vance. His “Planet of Adventure” series is as good as scifi gets.
I also highly recommend “Star Smashers of the Galaxy Rangers” by Harry Harrison for a different view of space opera.
Well hell since I got started I have a bunch that are my faves.
Startide Rising/The Uplift Wars - David Brin
The Demon Princes Series - Jack Vance
A Fire Upon the Deep - Vernor Vinge
Hyperion - Dan Simmons
A Talent For War -Jack McDevitt
Abyss of Light Series - Kathleen O’Neal
The greatest time travel story ever written: Dinosaur Beach - Keith Laumer
I’m not not navel-gazing scifi at all so most of the novels on these critics’ lists are too self-absorbed for me.