"BTC's longterm security depends on people paying extremely high TX fees which won't happen in a free market."
This is basically the new "bitcoin is bad for the environment" FUD that started a while ago to also justify the ongoing spam attack against Bitcoin that is known as Ordinals.
The flaw in this types of argument is that they forget the
price.
You see, miners don't pay their bills in bitcoin, they pay it in fiat. So if they earn 1
BTC they pay the same electric bill in fiat (eg. $100) than if they earn 1.2
BTC with fees. That means if bitcoin is worth $120 they are already making a profit ($20) and if they earn 1.2
BTC they make a bigger profit ($44). In other words they don't
need that extra income generated by the fees.
So far the price has been on the rise in the long run (in each halving cycle) and you can't find anybody who would argue that the rise is going to stop here and never go up.
Keep in mind that this is for the near future, like next 10 years. Anything beyond that (like speculating on year 2140 where there is no more coins left to mine) is silly because it is impossible to know how the cryptocurrency and cryptography scene is going to be beyond next 10-20 years let alone talk about 100 years from now!
Bottom line is that high fees is a problem that needs to be fixed specially when it is caused by a spam attack like Ordinals that is exploiting the protocol and is abusing the bitcoin blockchain.
I agree with you, if mining is not profitable logically Bitcoin mining will stop forever from yesterday or today. In fact, more and more new and old miners are expanding their scale. And I am sure that the miners are not stupid or lack knowledge, many of the miners are currently using green energy and environmentally friendly solutions, noise problems and other environmental problems are always being improvised or updated to make them environmentally friendly, even at the level of countries or world governments. also contributed to the improvisation of environmentally friendly Bitcoin mining
Apart from that, regarding what the OP said regarding transaction fees, Bitcoin transaction fees do go up and down but tend to be stable at around $2. The spike in transaction fees that we experienced up to $20 only occurred for a few moments and was not permanent, this is indeed a problem but not that serious considering that even with low fees we can still send Bitcoin even though we have to sacrifice time which can reach 1 week for transactions BTC confirmed. I'm sure Bitcoin developers are still racking their brains to make Bitcoin even better in the future.