I can’t speak to rbenv or npm, but IMO it’s better of use well known and canonical tools for each rather than a more unknown mega tool that wraps or replaces these.

pyenv isn’t perfect, and isn’t what I’d use for prod images, but for dev setup it’s relatively bulletproof and less issue-prone than any alternative I’ve seen.

Been using pyenv daily for years now. In what way could it implode? It's worked great so far.