Dex fee are stupidly expensive, due to ethereum gas fee and the current popularity of decentralized finance as the fees spike over 500% in one month, for now it's not recommended for day trading or for trader just in general. The good think is Ethereum 2.0 getting closer and closer as it will reduce the gas fees and hopefully in the future the Ethereum technology will keep improving and maybe Dex can even be a first choice for trader.
Ethereum 2.0 is not the only thing that will help with the high transaction costs. As I read somewhere, Uniswap is developing it's v3 which will rely on the layer-two solution that could help improve transaction speed. For example, xDai chain is layer-two solution. It is an Ethereum sidechain that can proces transactions at the speed of 60 tx per second, while Ethereum can process about 15 tx per second. So you see, it is four times faster than Ethereum and I'm pretty sure once Uniswap v3 goes live, it's volume will skyrocket.