However it didn't gain traction (probably because you need to run full node)
Or just because there isn't much concern. The game theory discourages all kind of attacks. Not just of an outside attacker.
Yes, let's go back to the PC and maybe GPU. The original idea of Bitcoin and PoW are using the spare computation of PC, right?
That wasn't the original idea, but it does form a more decentralized network, yeah.
If the "enemies" are using the PoW computation, they would have nothing to complain.
I'm not sure I make sense from this. What do you mean "to complain"?
For decentralization, you definely want a PoW with no mining pool.
Mining pools are necessary for low-capital miners to have a steadier income. What's needed is to discourage centralized pools' malicious reorgs further.