Ethereum clearly has issues, but will not easily be replaced. It takes a lot of work to switch to another Blockchain, so I would think that teams would only switch if they see their project fail if they stay on Ethereum.
Also if you want to do an ico for your project, then investors can easily change their fiat money into Ethereum on coinbase for instance.
If people first have to get bitcoin or Ethereum and then switch that into another coin, on binance for instance, before sending it to you for your ico, then that is an extra difficulty that will stop some investors from investing in you.
In marketing we know that distribution and availability is important.
App builders choose to build on Windows, iOS, Android or Linux. None of them are going to disappear anytime soon. I think the same is true for Ethereum.