A common reason for breakage is/was:
- Neovim changes some API (deprecating, ...).
- User upgrades Neovim and theres some incompability, OR user upgrade plugin and that plugin assumes a much newer version of Neovim. (I've often seen Neovim plugins "mandate" either the latest stable Neovim or even HEAD).
But: 1. Neovim has been including some popular plugins (or at least their functionality domain) in the past few years. This obviates the need for plugin-for-$THING, and reduces breakage.
2. ISTM that the pace of (new) plugin development in the Neovim-sphere has slowed down.
The latest example of #1 is vim.pack, which is a plugin manager similar to vim-plug, mini.deps (vim.pack is based on mini.deps), lazy et cetera.I can remember removing vim-commentary (from tpope) a while ago because Neovim included something like it in the main distribution. Granted, that specific plugin never broke because it uses the stable viml API.