Stagnant? Bitcoin doesn’t need to change. Bitcoin actually has the fastest SETTLEMENT times compared to ALL coins. Bitcoin Cash and Litecoin settle more than 10 times slower than Bitcoin. Compare how much shitcoin confirmations is worth in just one Bitcoin confirmation.
Do you know how many code changes Bitcoin had since it's creation? It's changing all the time and that is the rule for anything in life, adapt and change or die.
Even now we are going to see Taproot code update soon, and I am not at all comparing Bitcoin with any altcoins, but I was talking what could happen future.
If you look at the bigger picture and all climate change plans by 2030 you would realize that we need to start thinking of ways how to improve and change PoW.
Again, I am not saying Bitcoin is the source of problem with spending only 1% of world energy, but we better be ready for some bad scenarios.