I would use cash today if I didn’t need to deal with stupid amounts of change. I don’t carry a coin purse and I don’t want to, and I prefer my wallet to be thin instead of packed with bills. Some solutions (in the US):
abolish the penny - ideally we’d abolish the nickel and dime as well and round to the nearest $0.25
include sales tax in the price on the shelf - buying a $0.99 item ends up being $1.08, which means I get a handful of coins with nearly every purchase; if it was included, stores would probably round and eliminate most of my change
have better security on debit cards - I don’t use mine because of horror stories around fraud; I’m thinking banks would generate a special token for each vendor (i.e. a separate card number) and the user would set a limit on it; if the UX was decent, it could go a long way; if there’s a breach, attackers would only be able to spend up to that limit, and only at that vendor
I’m sure there are a million ways to improve things, yet we do none of them. But until cash stops being a nuisance, I’m not going to use it.