Formally, proof-of-work crypto is proof-of-energy crypto, and energy is perfectly valuable thing. The problem is that you can't extract that energy back to utilize it for your needs.
Proof-of-stack crypto is obvious scam, so not need even to take it into account.
There could be another crypto with proof-of-networking, i.e. mining occur when node service network long enough, i.e. you getting new coins for supporting network activity and availability. It shoud be much less energy hungry, with much more sustainable network and nearly instant transactions. This will be "proof-of-time" kind of crypto.
In any case crypto, while backed with some real values like energy or time, which means every single coin was not made "from air" like fiat, still have a problem with extracting its value back. It's like making coins from gold without ability to make a raw gold from coins.
So, there is still long enough way for independent currencies to go. Wile it have limited, but decent use as an alternative payment system, crypto is in no way perfect. It's just a beta version of independent currency.
Precious metals are far from perfect too. Just a simple problem with precious metal verification, when you don't have a simple way to check if coin/bullion is really made from precious metal with necessary purity makes gold limited currency too.
A fundamental problem with proof-of-work (or any proof-of-energy system, really), is that they favour the existing unequal distribution of wealth. The people with the most access to the ability to do computing work, or the most energy, are the existing rich. Obviously, the billionaires of the world can easily afford access to vast computing power that ensures that they would be the ones that would gain most of the newly minted cryptocurrencies.
So, even with the end of fiat and all money is now crypto, lo and behold, the current billionaires are still the billionaires and nothing has really changed. Except maybe people are more dependent on energy, computing resources and access to the network to do something as trivial as buying something, giving the billionaires even more power to de-person anyone they don't want, by denying them access to these things that a person cannot produce by themselves.
Your proof-of-network might be an improvement on this but I'm not sure it really fixes the problem. How hard would it be for a billionaire to own millions of nodes on the network? It's simply a matter of devoting computing resources to running independent nodes instead of calculating hashes.
How hard would it be for a billionaire to own millions of nodes on the network?
It could be limited to IPs, IP ranges or even AS, so IP, IP range or whole AS with multiple nodes receive as much as single node in IP, IP range or AS. So there will be no any reason even to buy IP ranges or Autonomous systems, since it will not give billionaire any advantage over average regular user running node at home, because all his nodes will be accounted as one.
It could be limited to IPs, IP ranges or even AS, so IP, IP range or whole AS with multiple nodes receive as much as single node in IP, IP range or AS.
But this would now limit the ability of an average user to run a node at home. If me and my neighbour have the same ISP, we will likely be on the same subnet and thus function as only a single node. So one node is effectively redundant and will receive no reward (or the reward will be divided). On the other hand, people with control of the IP address allocation will have the ability to allocate themselves a node on every subnet. This likely favours those with control of the network infrastructure, i.e. tech companies who are in turn owned by billionaires. Not sure this has really made anything better.
Formally, proof-of-work crypto is proof-of-energy crypto, and energy is perfectly valuable thing. The problem is that you can't extract that energy back to utilize it for your needs.
Proof-of-stack crypto is obvious scam, so not need even to take it into account.
There could be another crypto with proof-of-networking, i.e. mining occur when node service network long enough, i.e. you getting new coins for supporting network activity and availability. It shoud be much less energy hungry, with much more sustainable network and nearly instant transactions. This will be "proof-of-time" kind of crypto.
In any case crypto, while backed with some real values like energy or time, which means every single coin was not made "from air" like fiat, still have a problem with extracting its value back. It's like making coins from gold without ability to make a raw gold from coins.
So, there is still long enough way for independent currencies to go. Wile it have limited, but decent use as an alternative payment system, crypto is in no way perfect. It's just a beta version of independent currency.
Precious metals are far from perfect too. Just a simple problem with precious metal verification, when you don't have a simple way to check if coin/bullion is really made from precious metal with necessary purity makes gold limited currency too.
A fundamental problem with proof-of-work (or any proof-of-energy system, really), is that they favour the existing unequal distribution of wealth. The people with the most access to the ability to do computing work, or the most energy, are the existing rich. Obviously, the billionaires of the world can easily afford access to vast computing power that ensures that they would be the ones that would gain most of the newly minted cryptocurrencies.
So, even with the end of fiat and all money is now crypto, lo and behold, the current billionaires are still the billionaires and nothing has really changed. Except maybe people are more dependent on energy, computing resources and access to the network to do something as trivial as buying something, giving the billionaires even more power to de-person anyone they don't want, by denying them access to these things that a person cannot produce by themselves.
Your proof-of-network might be an improvement on this but I'm not sure it really fixes the problem. How hard would it be for a billionaire to own millions of nodes on the network? It's simply a matter of devoting computing resources to running independent nodes instead of calculating hashes.
It could be limited to IPs, IP ranges or even AS, so IP, IP range or whole AS with multiple nodes receive as much as single node in IP, IP range or AS. So there will be no any reason even to buy IP ranges or Autonomous systems, since it will not give billionaire any advantage over average regular user running node at home, because all his nodes will be accounted as one.
But this would now limit the ability of an average user to run a node at home. If me and my neighbour have the same ISP, we will likely be on the same subnet and thus function as only a single node. So one node is effectively redundant and will receive no reward (or the reward will be divided). On the other hand, people with control of the IP address allocation will have the ability to allocate themselves a node on every subnet. This likely favours those with control of the network infrastructure, i.e. tech companies who are in turn owned by billionaires. Not sure this has really made anything better.