If there is no fee, the mempool will completely be congested.
Exactly, and I could do that with a few hundred dollars in satoshis, how would miners then prioritize transactions to avoid spam?
Go back to blacklisting and turning Bitcoin into Bank of America?
Fees are necessary evil unfortunately!
But maybe profit is possible as people will pay higher transaction fee.
Not a maybe, it's for sure.
https://bitinfocharts.com/comparison/bitcoin-fee_to_reward.html#3mRight now fees are around 10% overall but with peaks reaching 1.82
BTC, closer to one-quarter of the reward for small intervals.