>>281158278
Original goalpost was
>bad guy shows up
>unlock new transformation to beat him
Which is wrong

I'll just examine your post more than this because it highlights some bigger issues though.

>that's just the arc i watched
You're judging a story disconnected from larger context
>i watched
You're watching Dragon Ball instead of reading it, which is a huge issue in itself

The Cell arc actually has a bit of an issue with its structure. It starts with interesting ideas and subplots. The androids that show up aren't the good ones. The androids can hide their ki and absorb yours. Android 20 is actually Gero, and they have to find his lab. Why is 16 deemed a failure and what's with his personality? More important than any of that, what's with this new time machine that came from 3 years after Trunks' timeline? Can they catch Cell before he can eat more people?
All interesting things. But then it's traded for powerup ping pong in the middle of the arc, which is kinda lame. It still doesn't fit what you're describing but there are issues with this arc.
The Namek arc is handled a lot better since the characters can actually achieve things that aren't defeating the main bad guy. It's easily one of the best arcs in shonen period.