In 2017 and 2018 and partly 2019, ethereum fees was relatively cheap, but immediately the rush for Defi started, the ethereum network couldn't handle the volume of it users because it can only process 15/TPS. It could have even been worst than we are seeing if not for offchain transactions and other blockchains handling defis, NFT, gaming and the newest the Metaverse. In the future Eth should be able to migrate from POW to POS, then we should start enjoying low fee again.