You aren’t wrong about your observations. Welcome to Home Assistant. Something to note, there’s a very clear difference between supported integrations and custom integrations.
The supported integrations (such as the one you installed for SmartThings or possibly your Honeywell Thermostat, as well as major platforms like Hue, ZigBee or Z-Wave) are going to be supported right out of the box and are subject to approval to merge from the Home Assistant developers in the github repository. These typically are monitored for things like how many folks are using it, what kinds of errors may be going on, did the vendor change the API etc, and get attention from a team of folks. These integrations also have to adhere to set of standards, like clear documentation, multi-language support, general supportability, and avoid doing things like scraping websites or other things that just don’t work well or might make Home Assistant a target for some company’s lawyers which no-body wants. Just look through this file and you’ll see the people who are marked as the person or persons who originally wrote and or support the integration. Several integrations have multiple people meaning more than one person helps to maintain that integration or approve changes. The full list of supported integrations are here.
Integrations - Home Assistant (home-assistant.io)
When you get to custom integrations (the ones you install through HACS like the FGlair Integration for example), then it’s a little more wild, wild west. In those cases, the developer might just be one person, a hobbiest like many of us, and may not have the time, ability or desire to write clear concise documentation and may assume users are advanced and know and understand things or take things for granted. I’ve seen it all the time. Thing is, most of the time, you can get a hint about an integration based on things like how many open issues are there, are they getting closed or addressed, when was the last PR merge, tells you a lot about an integration and whether or not it is still maintained or not. If it is maintained, I think you’ll be surprised how starting a question with “VERY new to HA here, but was trying to get this working, and I tried this and this and…” will illicit a friendly and helpful response. Not always, but most folks are pretty eager to help a newbie out. Just be clear in what you are doing, help them see what you tried and someone is likely going to try and help.
For example, I looked up FGLair and I found this community post
Home Assistant support for Fujitsu General Airconditioners [FGLair] - Share your Projects! - Home Assistant Community (home-assistant.io)
which lead me to this github repo
pyfujitsu_for_homeassistant/README.md at master · Mmodarre/pyfujitsu_for_homeassistant (github.com)
So this is definitely and advanced thing. First off, this particular repo hasn’t been updated for 5 years. That’s probably a red flag #1. Second, if you look at the forks you can see that there is one fork which was last updated 10 months ago. Third, if you look at the issues, you’ll see the latest issue has a solution which points you to bigmoby/fglair_for_homeassistant: FGLair heat pump controller integration (github.com)
This one was last updated last month, so is likely gonna be at least somewhat working. With custom integrations this happens all the time, the OP made a thing, got bored with it, hasn’t updated it for 5 years, and someone else forked it, took it over and is doing their own thing with it. Unfortunately, you are right, this isn’t beginner stuff and does take a bit of digging to figure out and requires some knowledge about github to get a hunch about a lot of these things.
The difference between the supported and the custom is that there’s simply not enough time to allow every custom integration to become supported. A lot of them do, but they typically have to go through code review and approval, meet the threshold of standards etc before it can get merged in, and a lot of folks just don’t wanna spend that time to do understandably. So lots of folks leave it as custom and maintain it for themselves. But custom integrations tend to get updated very quickly because they don’t require the amount of additional code review or approval to get published. Lots of custom integrations I’ve seen a bug filed and the fix is available within hours.
What I’ve found from my multi-year journey to Home Assistant is now before I make a purchase, I check Home Assistant Integrations and look for a standard local (non-cloud dependent) integration and that really does sway my purchase decision. I also look at the stats and see how many folks have that integration installed, that typically gives me an additional sense of security that I’m not going on my own into something. I get how this isn’t possible in retrospect and what you have in your house for HVAC isn’t something you can simply change overnight.
Sorry for the long ass post, but I hope as a new person it helps to clarify some of the challenges you’ve observed.