To be fair, what do you mean when you mention that XP has compatibility?
I didn't mention anything of the kind. I think you're confusing me with someone else. It does, but I didn't say it.
How does including backwards compatibility cripple an os?
Fairly obviously, by forcing it to be much larger, bloated with additional functionality that hardly anyone is ever going to use and most users won't know how to disable even if it's possible.
Hell, even some stuff that came out in 2000-2001 is having trouble working with XP. Is that what you call a compatibility?
Such as?