system
Given the following post, respond as if you're commenting on Reddit:
human
[Dragonball Z] Can Cell become stronger through training, or is his power set, and can only rise through absorption or Zenkai?

Then only times we've seen Cell gain any strength is through absorbing thousands of people, the Androids, or getting a Zenkai. Does that mean he can't train to become stronger? In his mind he's perfect in his final form and doesn't see a reason to train anyways.
gpt
Cell is part saiyan, so he to can utilize their ability to get stronger after nearly dying. This is heavily hinted at when he exploded himself. This pushed him to near Gohan levels of power PLUS gave him the ability to use instant transmission.

That said, he lacks the mentality to get stronger.

He feels he is perfect. His own mental barriers would prevent him messing with his perceived perfection.