Bitcoin is such a novel organism so the most worrisome at this moment is the unknown. And most particularly in my opinion, the unknowns which are hidden within soft forks such as taproot and segwit. They brought unforeseen consequences with them, and there may be more consequences that have not yet made themselves apparent.

Taproot for example improved various aspects such as privacy, but it also allowed for ordinals to be stored on-chain, which I consider to be an attack disguised as "fun collectibles".

Bad actors can put a lot of crap on-chain and therefore it could massively increase the cost/capability for the standard person to run his own full node.

Runes are a different example, which is a spam on the network itself, dramatically increasing fees and making it harder for users to transact on-chain. This one is less worrisome I think, because the cost to keep up this spam is not sustainable, but it is still an attack vector nonetheless.

Since I'm writing anyway, I'll quickly mention one thing as to one of your worries: Bitcoin's climate impact.

Look up the youtube docu "this machine greens". It shows a few of many examples of why Bitcoin will actually be a positive thing for climate (I don't recall if it was explained properly in that docu why Bitcoin will put an end to traditional warfare so it may require prior knowledge on that)