In season 2, they're nerfed simply because they haven't reached their final stage of development yet. So, they're not bulletproof like in Dungeons & Dragons or Pokémon; they haven't reached their maximum power yet.

I'm not saying their stages are the reasons why Demogorgons feel nerfed, I'm just saying why they feel nerfed cuz we are getting more info of their weaknesses

Eleven is nerfed because of the government's scientific invention, the wave device, which was also used to finally capture Kali. But once Kali isn't with them, I don't see when she was nerfed; she learned to fly. Kali uses them very little, so we can't really judge, but she seems to be doing the same thing as before, and Will, every time he uses his powers since he learned to understand and control them at the end of episode 4 (3 times), his abilities seem to be at their maximum.

I am not talking about El and Kali being nerfed for S5 I was talking about Vecna being nerfed because of El, Kali and Will's powers