VLC used to be the dominant video player for this reason, but then everything has crystallized around h.264 (and h.265) which made the breadth of codec support not as important anymore, making VLC slowly losing relevance because they aren't focused on user experience enough.
You say that but just yesterday i used VLC to play some old videos i had which AFAICT were in RealVideo format or something like that.
And i transcode everything i want to watch in my Android tablet (where i also use VLC) to mpeg2 because the tablet is ancient (10+ years old) and can't handle anything newer, so i am glad that VLC a) still works on the ancient Android OS it has and b) still supports an old outdated but CPU light video format :-P.
> slowly losing relevance
Installing VLC used to be one of the first things people did on a new computer, including many non tech-savy people, along with a web browser that isn't IE/Edge.
Now the fraction who bother installing it is much smaller. The default video player is good enough for most usage (overall usage has declined anyway because of streaming).