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.