I think Neovim itself has been stabilizing quite a bit in terms of upgrade breakage.

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).

  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.

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.

Yeah the lack of basic features in core meant core functionality was forced to use plugins with varying levels of documentation and commitments to stability (in some cases sending breaking changes before the supported neovim version even reached the arch repos). I'm glad to see neovim is improving in that aspect.