Problem with understanding ERC tokens

I want to let you know I tried doing my own research but I’m stuck on this part with my understanding.

I’ll see projects for ERC tokens like Quant and how they are these revolutionary projects only later to find out they are ERC tokens and not their own blockchain. If that is the case, wouldn’t these tokens have the same capabilities and limitations as a regular ETH coin?

To my understanding a token issued on a block chain would be limited by the technology of that blockchain it’s on (Gas fees with Quant and other ERC tokens are still high for example). If someone wanted to make their own fun token for something (Shib for example) I could understand making a token, but when I see solid Ethereum projects like Quant I think “why wouldn’t they make their own blockchain?”

Sorry for such a noob sounding question, but this is probably my biggest knowledge gap with crypto.