You need to swipe over 50% of the screen to close a tab by swiping, which is way too much. I usually don't even get to 25% and it works just fine with most browsers.

I totally agree with you about this and it annoys me as well. It shouldn't be too much work to change this, I will take a look.
@ekager has a PR open for this 馃槃
https://github.com/mozilla-mobile/fenix/pull/3770
Welp, less work for me then ^^
I will convert this to a UX review ticket so we can revisit the sensitivity after Emily's PR!
I suggested "Use the same swipe sensitivity as is used in Android notifications" in #3747
@topotropic can you review emily's update and if the sensitivity is as you expect, please close this issue.
@ekager's update was just reverting the already problematic swipe sensitivity. That was less bad than before the revert, but it isn't "fixed" yet.
Will be addressed in #3770
Most helpful comment
I totally agree with you about this and it annoys me as well. It shouldn't be too much work to change this, I will take a look.