I've been a staunch supporter of the browser "Doesn't Work" for years and years, and I still have to have "Ugly" and "Spies On You" installed.
• 20% of the reason is bad web devs making sites that only work with "Spies On You"
• 80% is that "Doesn't Work” has always been flaky and buggy and Apple seems uninterested in fixing it. Frequently just stops rendering and requires restarting—for YEARS. Add-on ecosystem results in constant breaking/restarting.
Mobile "Doesn't Work" is actually solid.