I identified [0] the source for much of it (sub-shells and pipes) and began a PR [1], but became bogged down with BATS testing, and then found mise / rtx, so kind of lost interest. Sorry. You can always implement these if you’d like.
[0]: https://github.com/asdf-vm/asdf/issues/290#issuecomment-1383...
asdf hasn't just started getting popular. It's been popular for a long time already. IIRC I started using it ~8 years ago (~2016). asdf has been around since 2014. I believe Mise (rtx) has been around for a couple of years already too.
Also, contrary to the other comments in this chain I don't find it particularly slow..
People will generally change taste and likes/dislikes every few years.