So much! While D&D is certainly one of the biggest names in the TTRPG world, there are as many gaming systems as there are ideas, from games based on books/films/TV/anime to original concepts.
From more established gaming systems like Pathfinder and Numenara to small digital-only games like Faceted and Masak Ayam, there's a game out there for everyone. There are games with complicated rules systems and intricate worlds and others with very simple setup and silly concepts. There is a quickly growing market for TTRPGs outside D&D, so more and more are getting print editions you can purchase a variety of ways.
One of the benefits of trying games outside of D&D is learning more about being a good player or game master (GM), and really finding what kind of story you like to experience as either. Some people like really technical, math-heavy games as players but would much rather play something light on rules or math as a GM. The best way to find out is to try, and that process can be a ton of fun.
Pathfinder was made by a team who previously worked on D&D, but wanted to go a different direction. It's a bit more technical than the current edition of D&D, but even as another fantasy TTRPG has a ton of different options and approaches to things compared to D&D.
Also, the creators of Pathfinder made Starfinder, a sci-fi game that uses the same framework as Pathfinder, but also includes options like building space ships and exploring planets or entire galaxies.
Top 10 Games covers a particularly interesting thing about TTRPGs: you can play them by yourself. There are tons of games out there meant for one player! Take a look at this one and see if maybe that's the kind of game for you.
There are so, so many ways to access TTRPGs now, and some even involve interacting directly with the creators of the games, giving them feedback or suggestions to refine the game further. One thing to keep in mind: these sites generally have paid content, so do look at prices. Some games or content is free, but others can be more expensive, especially if there's a print edition of a game available.