Huh, same here! I have it on GBA and have been periodically playing it since I was a kid, but I’ve never actually been more than 2/3 or so in. I was never able to put my finger on why - it seems like an amazing game with its charming aesthetic, good controls, it does a lot of things well - but now that you say it I think you’re right, the level design and emphasis on checking every nook and cranny really does make it kind of a slog. I just booted up my last save and played a bit of the next level, and the amount of backtracking, secret side areas, and mini puzzles is kinda overwhelming.