is it me, or are a lot of ufc fighters a bit brittle?

man alot of them arnt even kos they are ref stoppages. the thing is anytime you get knocked down is a partial ko and after 5 seconds to get up is a full ko boxers get koed multiple times in fight on a physical level but continue fighting because rules wise its not a ko. at the same time boxers spend years developing thier chins in amatures and low level 4 round pro fights. in mma there only one level pro. the difference between any pro and amature mma fight is one you dont get paid. also theres no like 2 round fights or anything to build up. alot of the guys go from grappling to mma never having been hit. they arnt brittle just green and often fed to the wolves.