I think using a couple of overpowered mods all time takes the fun out of the game, but using them once in a while just for fun, testing or such is very good.
I remember when i played Minecraft for the first time, i didn't know that mods existed, it was really fun, i was a noob and made dirt houses which creepers blew up all time, and that is what is fun on the game, it is somehow better when you don't know much about it, you explore and learn more.
Then like 6 months later i filled up my Minecraft with mods, too many items, single player commands and some other i can't remember of, it was no fun at all, it took out all the challenge and purpose of the game, so i kinda agree with you, overpowering mods all time take out the fun.
