Shouldnt the same exercise get easier over time? ( eat good and sleep good )

My routine for two years have been.

I run at the park, the same route every other day same with 100 pushups! However it never gets easier, and i am stuck at 25 pushups per set and then my muscles give up ( i can not do a single one more ) for quite a while like 3 min then i do 25 again. Good days 1 min between sets.

I have tried not doing it everyother day but i get weaker then.

Shouldnt you get better doing an exercise after a while, like even simple exercises? Maybe it tskes 2 years for people to improve?

I am asking since historically everyone who asked similar wuestions just get answers about diet and shit, but i eat very good and i should not need a rocket science diet when i eat the same things as my friends that build muscle and i do go up in weight..... in fat. So please be respectful and no diet talk.

My test levels are normal.