I think most of the complaints about moment are that it's really big (because of i18n and timezones). Obsidian isn't a web page/app, so it doesn't need to optimize bundle size too much.
It's unexpectedly mutable unless you've closely read the documentation, been bitten by the mutations, or are doing very simple date manipulations.
It's a great library, but it does need fewer footguns. date-fns is a good alternative.