It is not profitable to trade tokens in the Ethereum ecosystem, because the cost of an exchange on decentralized exchanges is from $ 50 to $ 100 or more.
If you change for amounts of $ 5,000 or more, then for you this is a small fee for decentralization.
It is not easy to handle too expensive fee like this. Even if I have a good capital and make a transaction at $5,000, $50 or $100 as transaction fee is still bad cost.
This expensive fee put projects have to build up bridges between ERC20 and other chains that can provide lower transaction fees for users. ERC20 is still a big chain and I hope upgrades in future can help them to scale up their network as well as reduce transaction fee successfully.
I know about Polygon but did not know about Optimism or Arbitrum. Thank you for this info and I am sure will do my research on these projects.