When I work on Cave Story mods for a long time, I always lose motivation, especially from people trying to bring me down. Whenever that happens, I always work on something else for a little while as a break. Maybe I'll work on a different mod, maybe I'll work on something else entirely, and I always find motivation again
I suggest you try to find the fun of what you liked in Cave Story modding, do it as a fun side project so you don't lose the fun of it, take frequent breaks and show it off to your friends or people to have opinions. No need to take it so seriously.