A diamond level player should be able to stop cannon rushes, maybe even a plat level player, although you might catch most of them by surprise because they might not expect a diamond level player to do that lol
I was playing unranked a few days ago to get some practice in before playing ranked again and someone cannon rushed me, he built the pylon in my base but i killed his probe before it finished, i blocked the front of my base completely while his pylon was building and he just left when he couldnt get a probe back in
He was either silver or unranked though so his cannon rush probably wasnt the best way you could do it
Another game i played had someone try to void ray rush me but i scouted it and was able to stop it completely, another game had someone using blink stalkers to harass my probes and i was able to save most of my probes and managed to eventually win since he didnt have much economy or much of an actual army since he didnt do enough damage with his harass
Then i lost to a plat because when i scouted his base i saw him hide a pylon to the side, i assumed he was going to hide some sort of tech, like a stargate or something, so i thought there wouldnt be much early aggression because he was going to hide tech, but after i scouted him he went 4 gate all-in and since i expanded i had nothing to even try stop him
I saw you on the other day bacon, i said hey like 3 times and you never responded
Then you logged off
I guess you were too afraid to face me in a 1v1 game