Afox
When you make changes that are specific to PHP 8.x some of those changes are NOT backwards compatible. We will not hack our code to support older versions of PHP, especially EOL versions like PHP 7.x. Your thinking is entirely incorrect here.
Maybe you should try to fork the osticket repo and maintain 1.15.x yourself to see how it goes if you think otherwise.
Also, be glad we now support 2 versions, we used to only support 1 version at a time. 😉
Cheers.