Let's see here...
The subject of the thread asks for "alternatives to 5E," and the original post asks for "alternatives to Wizards of the Coast," so I'm going to assume you are looking for a third-party fantasy RPG. Now, WotC is the largest publisher and D&D is the gold-standard for tabletop RPGs, but they are far from being the only game in town. You are going to get lots of recommendations.
I'm no exception. If you want to play something D&D-adjacent that isn't published by Wizards of the Coast, give
The One Ring a look. You might also like
Legend of the Five Rings RPG for more of a samurai-fantasy mashup vibe.
The 13th Age is pretty good, I hear, but I haven't played it. And I never miss an opportunity to plug
Numenera, probably one of the most underrated RPGs ever written.
But...
...and I hate to write this, but I've experienced it firsthand on more than one occasion...
...be prepared for disappointment. For better or worse, there isn't really a substitute for D&D. If you are looking for something that looks exactly like D&D, and plays exactly like D&D, and has just as many published works as D&D, and has just as many players as D&D, etc., you won't find it. There isn't a such thing as "Just Like D&D, but not D&D" on the game shelf--the best you can hope for is "Not D&D, But Close Enough For Me." I hope you find it!