Hi Toufiq and Paul.
I understand what you're describing and your opinions, but you know this is handled by industry-standard or average compatibility values.
The requested project required 10 years of compatibility, but we agreed to 9 (because SPPB 5.4.x was compatible). They said OK, we haven't had any problems with CSS. The problem is with Javascript, which in the 2017 browser console (version 55) gives errors such as "Uncaught SyntaxError: Unexpected token." And this isn't in the editor, but in the public area where any visitor has access.
That's why I'm asking, how many years of compatibility are you working with?
The question isn't about me; my computers are modern with the latest versions. The question is about our clients and visitors. Bringing Windows XP here makes no sense. No one mentioned 2014 or earlier.
Regards