This isn´t really true. The mempool only has a few thousand transactions most of the time these days
- since the spam attacks on the Bitcoin blockchain stopped.

Therefore even very low fee transactions with a few cents are getting processed in 1-5 blocks.

The reason why the average transaction fee is still so high is, because some users just don´t have
a clue that they could get away with a much lower fee and the fact that many wallets use terrible
standard settings for fees (and the average user is lazy and doesn´t bother to customize the settings).