I think YNAB's popularity comes from the stand-alone desktop version which was really popular until they went cloud.

I'd have to disagree with you. There's tons of people who use them as a mobile-first service (my wife only ever uses the mobile app). I think a subset of tech/privacy savvy people don't like that they went to a cloud based model, but that's a small subset of a small subset.

Mint is another example of a popular financial management tool, that was always cloud-first. It would import transactions by using the same credentials you would use to login to online banking. This wasn't appealing to me. This didn't deter many other people.

I didn't like sharing my credentials either but I was using it – until it stopped working for most of my accounts.

I've since stopped using even the 'manual import' and I've found that reconciling to my bank/financial-company statements manually is much easier overall as importing auto-reconciled transactions but then it was basically impossible to then match any specific balance reported by the bank/financial-company.

To be fair, Mint was a mistake. It was always a mistake. Being ahead of hackers' time, it was successful. This is the only reason.

At least in my case, it's because I don't know of any better options. Mint is very easy but if something else was almost as easy but provided similar features (or more, even) I'd give it a sincere try. But other options I've heard of are cli tool/emacs packages, which is too much to ask for what is usually less robust and requires significantly more effort/time to get up to speed with and use.