Sssh. It is important that the world burns for some rich dude's fake money.

The idea behind using distributed compute nodes for blockchain was that the blockchain itself would carry applications with commercial value, and the token itself would represent a share in that commercial value which would scale accordingly. There would be no reason to mine coins if those applications never materialized, so effort would always track alongside the intrinsic value of the network itself.

Bitcoin never developed any real applications, and the entire value was speculation. This meant people raced to mine coins as fast as they could, well beyond the intrinsic value of the app stack (which doesn't exist). So now the network has effectively collapsed for all intents and purposes, but it is still needed for moving Bitcoin around, so the people who have huge investments already basically have to keep throwing money at mining in order to preserve the "liquidity" of their current stash.

So then Bitcoin mining only makes sense if you also heavily invest in the energy company

Correct. Buying your own solar panels or wind turbines. Your mining rig only makes sense when your expected return from the rig is greater than the return you could get from backfeeding the grid.

Or if you can somehow make use of the "waste" heat, perhaps by heating your home, or preheating water before it reaches your water heater.

Between this and the AI bubble, there has been a tremendous flight of capital from the middle and lower classes to the parasite class.

And you're dead on with the human centipede corollary - once money enters the vortex it stays there until it gets excreted in some unholy fashion. Like private armies and rape islands.

[...]problem is that difficulty adjustment is not automatic and its done only once every few months so [...]

Last time I checked it was automatic and done each 2.016 blocks, which should ideally take 14 days time (10 minutes per block at average).
When the difficulty gets adjusted, it gets automatically set to a level, which would take exactly 14 days to mine the next 2.016 blocks.
https://en.bitcoin.it/wiki/Difficulty

I'm no friend of PoW in general and even less so of the way Bitcoin implemented it (resource hungry arms race for specialized hardware compared to PoW done only by general computing devices cough Monero), but insinuating there'd be some manual adjustment is disingenuous.