User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:89.0) Gecko/20100101 Firefox/89.0

Steps to reproduce:

Upgrade to 89

Actual results:

New version of Firefox lacks any contrast between active and inactive tabs - they look almost identical. Disabling proton helps and restores proper contrast.

Expected results:

There should be a stronger visual cue for the active tab. Generally, I think the new tabs are visually unappealing and non-functional... But lack of contrast is actually a usability issue.