that is not the whole story. in fact you have forgotten one thing because you are looking at the very recent history. in fact with price rise, fees have gone down in bitcoin terms. for example when price was less than $1 the fees were around 0.1BTC and as the price went up, the fees went down too. or a couple of years ago fees were fixed at 10k satoshi per transaction.

keep in mind that as far validity of a transaction is involved, the minimum valid fee is zero. it is the "fee market" that decides how much it should be. and fee market is affected by the competition (for the scarce block space) and the price.

immutable means "unchangeable", and immutability of bitcoin means its blockchain is not going to change.