Constant Errors and Low FPS Issues in League of Legends

I've been playing League of Legends for 2 years, but the issues seem never-ending. This game is so problematic that even Roblox runs more smoothly in comparison. Every time I log in, I encounter different errors, and don’t even get me started on the matchmaking system—it’s a complete mess. My friend experiences FPS drops to as low as 30 just by moving the mouse in-game. How can a game this popular still have so many unresolved issues? I'm beyond frustrated and can’t understand why these problems persist.