There are plenty of ways to avoid 1:1 mapping between keys and access to/control of things on decentralised networks and blockchains, so really these are not ar

There are plenty of ways to avoid 1:1 mapping between keys and access to/control of things on decentralised networks and blockchains, so really these are not arguments against blockchain just against a specific way you can choose to manage your keys. Simple multisigs are a good start, as is key recovery via m of n (Shamir's secret sharing). More sophisticated systems have been built on top of this to allow, for instance, users to use their (singular) keys and to also allow a process, that remains decentralised, in which multiple [somewhat] trusted parties participate to recover access if they lose their keys or die. These solutions are obviously more complex to build and interact with than a simple public/private keypair, hence why it has taken longer to develop them, audit then, and get to a point where they have a decent and intuitive UX (check out Argent, Gnosis Safe, among many). But if a big part of your argument against blockchain technology in 2021 is about lost keys, I'd highly recommend digging deeper into the state of the art before getting too stuck to a conclusion. There was a time "I wouldn't use my credit card on a website because it's too insecure" made sense too, but HTTPS became the standard and we moved on. So it goes.