It depends on who you talk to but OOP is still alive in the PHP framework crowd especially with composer and PHP8 is heavy on the OOP. Pure OOP creates too much surface area for bugs, more code, more variables, more everything. Its main benefit is that its easy to teach and its easy to read. It only seems like its dying because once you get past the easy stuff and start writing complicated code (libraries, games etc) you find that breaking code up into hundreds of little parts is not efficient or productive.