Maybe I need to elaborate that the scalability issue that I address here is not the same as the Bitcoin scalability problem (the limited amount of transactions per second on the bitcoin network) that is widely known and that structures like Lightning are trying to solve. It is a separate class of problems that arise in any distributed network with untrusted components, where the lack of trust is solved by letting every “full node”, “server”, “router” or whatnot listen in on every transaction. It is essentially a DDOS “attack” built into the protocol itself.
Mitigating this problem means reducing the amount of nodes that participate in every transaction, by whatever means — which decreases the security of every transaction, and not just for Proof Of Work-based algorithms. This is not limited to monetary transactions, but to any kind of decentralized consensus building in open to join / registration-free / pseudonymous systems, because malicious nodes can join and leave at any time with impunity.
In all honesty though, I fail to see the necessity or even desirability of such systems in the first place. What problem are we even trying to solve?