For now, our Metamask integration works only with the Ethereum blockchain since it is still the one most used.
True indeed but you should really consider implementing other blockchains as well. Ethereum fee is a pain in the ass.
We are aware of the high transaction costs of the Ethereum network but we believe that this situation will be improved in the future.
Did you mean the fee of Ethereum blockchain? I really see no hope unless Ethereum's price drops significantly. There was a plan for PoS Ethereum but that has been paused AFAIK. Therefore, it's not going to be improved anytime soon.