If you think a protoss unit is useless, try ranking out of bronze first.
Colossi - bye bye ling bane! Bye bye hydra lurker. Bye bye marine marauder push! Goodbye defensive bunker! See ya lurker! (colossi can get their 9 range upgrade way earlier than the lurker one). The cliff walking feature is very macro-able, think about that when you start complaining again.
Immortal - roach ravager pushes squished when combining with force field. Thors? Pfff! Out with that normie !@#$! Any kind of terran mech? SEE YA! Great at taking down defensive zerg and especially terran.
Void ray - Ultimate counter to terran mech. Terran’s viking might be 2 times cheaper, but a single void can take out 3 of them. Meh in PvZ, but can protect your skytoss real nice against corruptors.
Warp prism - are you kidding? Arguably the best transport unit in the game. Can switch between warp in mode for aggressive or cheesy attacks, pick up from MASSIVE distance (the most advanced form of macro in the game in my opinion) and even has its own speed upgrade.
In conclusion: u r bad. get gud