It's funny when your first sentence is taken literally. You would rather stop watching YouTube and then, be exposed to terrible ads.
it's "than", not "then". To know which one to use, prononce it like if it rhymes with "ban" - instead of "hen" - in your head, you'll know which one is correct
You can also look into invidious instances, if you want to avoid downloading an app.
https://invidious.io/
EDIT: Or piped, https://piped.video/