Economies of scale (EOS) is a barrier to entry... proof of work always benefits from EOS
Fortunately there are parts of our economy -- like computer DRAM -- that are much bigger than cryptocurrencies.
In order for the bitcoin mining industry to be as big as the DRAM industry each BTC would have to be worth $25,000 each. And that's only until the next halving, at which point the price has to be $50,000 each.
Proof-of-X for X!=Work is largely off-topic for this thread. Only POW serves as an origin of scarcity anchored to something
physical (computing devices).
The scarcity of BTC and POW systems has nothing to do with the POW algorithm and everything to do with the social contract of the nodes. Having studied POW systems for a very long time to build a memory-hard easy to verify algorithm... I believe I had a lot of success and with small tweaks could achieve it.
This thread, being about POW innovations is really aimed at network security in the most decentralized manner possible.
DRAM may be a much larger industry and it is unlikely an ASIC could be developed that is more effecient, but no ASIC needs to be developed for EOS to apply. You don't think someone could build a special-purpose motherboard / CPU designed to minimize overhead costs around the DRAM? You think large warehouses of case-less, power supply-less, liquid cooled, over-clocked, modules would not make mining at home unprofitable? You think bulk buys cannot make it significantly cheaper for these large factories?
The reality of POW is that security is proportional to economic cost and whether the attacker is spending $500 M on SHA256 ASIC or $500M on dedicated hardware the result is the same, $500 million being transferred from shareholders to miners while the network centralizes in the mining pools and barriers to entry are erected.
If you increase the cost-per-hash with memory-hard POW, you will get fewer hashes but the same level of security and only the most efficient operations will be able to mine profitably. Once mining profitability for the average home PC is negative the network is depending upon charity to remain decentralized. Sure anyone can mine, but not everyone can mine profitably.
With POW the network is not sustainable.