I haven't played this mod yet, but from what I've seen, at least some levels look pretty interesting. I'm playing the first mod right now, and I think many of the advanced levels are creative. Let me know if you want a full review of it.
My second level pack released two years ago. A few people have pointed out issues, and now even I can see problems with several of my released levels that I ignored or just didn't see while making them (for instance, some spots, especially in my second level pack, require too much precision and make gameplay finicky). I'm using those realizations to take better care while making new levels and hopefully not make the same mistakes again. My next level pack will undoubtedly have problems too—one level could be particularly easy to screw up—but if I enjoy making levels then it's not going to stop me.
I don't think you should be discouraged by the negativity or the bad things about your levels, either. You said right here, "It discourages me but I must keep going if I want to improve." So if you do want to keep making levels or working on a mod, then do it. If you feel like it, take a break first.
just downloaded and played it...played through all the tutorial levels and the first 50 beginner levels..ill finish it later (what i say might change after i finish the game)
most levels were unique and creative (though some just felt like filler)..some of them could've looked better aesthetically (mostly just texturing)
some of the scenery was really creative, i liked the ice blocks with the rings around them in "Tempest Wind" and the little box things in "Obstacle Course"..those were a nice touch, but some of it wasn't the greatest ("Bouncy Wind" literally just had super bounce dts copy/pasted all over the map.)
i couldn't really understand the theme of the game? some levels had really realistic skyboxes and it kind of went against the cartoonish style of the textures/levels....the cartoony-like skyboxes definitely suited the game better..
music is great. probably one of the strongest pros of this game actually...very enjoyable to listen to and doesn't get repetitive.
i loved some of the new ideas, my favorites being the bumper ring and the ice/snow wall and how you needed to break the wall using the cannon...that was a cool concept..
i also noticed you borrowed some things from roblox, like the sound effect when you pick up a super speed, and one level im pretty used a roblox skybox, and the other used gravity coils as its main scenery...not that im complaining or criticizing you, its just an observation..
overall i think its a good game, and keep in mind i only played like 50 levels. i wouldn't drop the project, i see potential in it..you just gotta polish up some things, that's all. don't get discouraged man.