I'd say that an OS is more akin to a scripting API or a programming language, which i am completely fine with.
modifications/plugins are literally just advanced scripts. some even are literally just scripts.
It's not ad-hominem because the analogue has direct relevance to the debate.
wow you're acting like such a capitalism here, continually defending your beliefs even when they don't make sense. (it is very relevant for me to ascribe your behaviour to that of a capitalist)
anyway, why are you so stubborn in your beliefs? you made this thread like a question, and then argue like it's a debate. if you really had genuine curiosity, then why do you refuse to accept the given answer?
is it because you're still curious on the specific details? well it's not like we're going to explain human sociology to you to say why humans want to have multiple modifications working together and modularly, with an easy and convenient way to achieve that. you've got the best answer we can reasonably give.