Their subscription model gives Unity the ability to change the TOS under dev's feet. [0]

Unity eventually walked back this change after a prolonged negative press campaign on Twitter, but counting on Twitter mobs to solve your future problems is a really bad business strategy.

I occasionally use closed-source programs for development, but I don't use programs where the output is constrained by a license, and I don't use programs where the TOS that binds me can be changed on a whim. I'll use a closed-source program like Aseprite or Reaper, I won't use Creative Cloud or Unity. The benefits aren't worth the risk.

[0]: https://arstechnica.com/gaming/2019/01/unity-engine-tos-chan...

Closed source.