I love Home Assistant. I only started using less than a month ago (moved into a new house). However, the two times i needed to upgrade Core (I use Home Assistant OS, their recommended installation procedure), it broke. The first time they had changed the spec of the 'correct' way of the YAML config file. Which means I didn't have an integration until i fixed the file manually (they deprecated something not gracefully…
I've been using Home Assistant for several years and I can count on hand the number of times I've had breaking upgrades. These were always pretty clearly explained in the release notes. I think the nature of the broad scope of Home Assistant is such that different users may have very different experiences depending on what integrations they use. But I don't think it's generally as bad as your comment suggests.
I think this is a common problem with "hub" projects that intend to bridge together multiple incompatible technologies. I work in VoIP and have been using Asterisk in one way or another for over 20 years. That project is even named after the wildcard character because originally it was intended to be able to connect any kind of telecom technology from analog to TDM to all sorts of VoIP.
As the world moved on and most everyone has standardized around SIP as the future those of us who run all-SIP systems and/or common analog/TDM interfaces have generally been able to upgrade willy-nilly with little to no trouble, but there's always "that one guy" who has rigged up something where a call comes in over a SIP-GSM gateway, gets sent over an H.323 trunk to another box elsewhere in the world, then rings to a SCCP phone and of course they're always having issues because no one else is doing anything close to that.
HA has that problem to an exponentially larger degree because at least the telecom world theoretically has widely accepted standards that most equipment uses where home automation gear has a few competing standards alongside hundreds of vendor-specific APIs that may or may not be documented or even officially open for use.
Someone who is just using HA to unify their lighting control across a few vendors using well-tested Zigbee and Z-Wave implementations is going to have a much easier time than the people who have rigged up a Rube Goldberg machine of integrations of varying quality.