You have good points about the physicality of cash and the guarantee that merchants will accept it. Crypto can be carried around physically with a hardware wallet, though it’s still not quite as good as cash in this regard. And that guarantee that cash is accepted comes with legal tender status. You can’t be guaranteed to be able to spend CAD in US for example, but plenty of the world has multiple legal tenders, see Europe.
I like cryptocurrencies, but admittedly they are still pretty clunky to use. Bitcoin has a lot of development momentum behind it, but I don’t see it as the feasible option going forwards due to the scaling shitshow and lack of privacy (no, taproot won’t solve this because you need privacy by default otherwise private transaction default to “suspicious”). Ethereum is great, I really like Vitalik’s leadership and it arguably has even more development momentum than Bitcoin. Unfortunately it also has the scaling and privacy issues like Bitcoin and additionally it seems to be primarily used to create pump and dump scam coins and shit like NFTs which are always going to clog up the base layer. Monero seems to have the most potential to me. It is like Bitcoin but has default privacy and on-chain scaling (we will have to see how that holds up under more adoption) without the dogma.