Bitcoin

Other coins have solved scalability, whereas Bitcoin is chained for the foreseeable future to its internal structure and cannot scale sustainably, hence its becoming centralized and using an ever-increasing amount of energy even though its transactions are not increasing, while transactions on other chains are increasing without a comparable increase in energy use. Since you mentioned XMR vs. BTC, which uses a CPU versus a GPU to process a transaction, much more energy is used by a GPU(BTC algo) than a CPU(XMR algo).

Your arguments against proof of stake(security, centralization, energy use) are problems that POW NFCs like BTC already have in spades, it's like arguing a hatchback is more dangerous than a sedan because the hatchback has four wheels that could pop at any moment. The sedan has an identical problem.

At the moment, XMR block size is 4x the size, occurs five times as often, and the xmr tx cost is 5000 times lower than Bitcoin, 1/10th of a cent(XMR) vs a little over $5.00(BTC). So even if XMR caught up to BTC price, that's less than a 200x increase, less than 5% the cost of bitcoin if the costs scaled as BTC has, which they would not do since XMR 1) is a different coin/algorithm and 2) has a deg team that is constantly increasing privacy and security while refining their transactions and their tx cost, which regularly decrease.

The important point here is that each coin is different and scaling up will not immobilize all coins the same way that BTC has immobilized itself.

This comment helps technically explain why with xmr specifically, unlike Bitcoin, equal use does not equal cost: https://www.reddit.com/r/Monero/comments/13deshy/if_xmr_monero_was_priced_the_same_as_bitcoin/

Basically, different coins use different algorithms to process cost, so due to the nature of each coin, no matter how many transactions you complete, the coins will function differently because of how each coin was created.

Your argument about scalability is like pointing to a flatscreen monitor and arguing that if the flatscreen ever gets as big as a CRT monitor, it will function identically. No, of course it won't, it is a different machine.

Coinjoin and coin mixers are fine for helping to obscure your non-fungible coins some of the time depending on the service, though the problem is not with the service but the coin itself they "mix", since coins like BTC are non-fungible, or uniquely identifiable as a function of their existence.

As a potential user, I don't see the point in using non-fungible currency that is so easily tracked and traced by literally anyone when fungible currency is available, unless one prefers more nth-party regulation over their finances and prefers anybody who has ever once made a transaction with you, or simply scanned your wallet once, being able to trace your transactions forever.

I understand that's what regulatory agencies prefer and that's why when state coins become more popular, they'll use NFTs like Bitcoin, but just being popular doesn't make it a better choice than many other coins, particularly as a practical currency.