WHY IS THE ‘VERB’ THE “KING” IN LANGUAGE?

Consider the following 3 sentences : John is playing the guitar. John was playing the guitar. John will play the guitar. These are the same things happening at different points in time. The separating or differentiating aspect of these 3 sentences is only time. So why does that differentiator have to be Linguistically manifested via the form of the verb only? Why not the noun or adjective or whatever? John exists today, existed yesterday and will exist tomorrow. The guitar exists today, existed yesterday and will exist tomorrow. The ‘playing’ (of the guitar) ALSO exists today, existed yesterday and will exist tomorrow. So why does the temporal differentiator have to be plugged into the ‘playing’ (verb/action) only? (when in fact all the 3 words - John (noun), guitar (noun) and playing (noun) are equivalent with respect to the difference in the time). Why not say that ‘John-ed plays guitar’ for ‘John was playing the guitar’, the “ed” indicating “John past”? Why is it so that whatever (that has an action/verb) that happens, becomes an “event/episode that happens i.e. verb”? (That is, say, why not “event-ed happen”?) Why does the verb carry the representative onus of the event (when there are other parts of speech hanging around)? Language is verb-centric.