Respectfully, that’s only one part of the picture. Luck is another big part of the picture. And the specific devices chosen matter as well.
There are many people who have posted to the forums who had really well set up systems that just stopped working one day because SmartThings ( or another company) had changed something on their side. This has happened multiple times to multiple people.
I’m glad that your system has continued to run well for you. I don’t doubt that at all. But a lot of it has to do with luck.
Just today there was an announcement that one of the most popular cameras in use with SmartThings in the US, Blink, is shutting down their integration with SmartThings. This week. 
As you know, SmartThings broke voiceover navigation in the official mobile app last April. They’ve said accessibility is important to them, they said they’re going to fix it, but here we are, eight months and several app releases later, and it still isn’t fixed. That’s not because I had my system set up incorrectly.
There have been similar issues with the Samsung television integration, which one would think would be a High priority. It worked, then it broke, they acknowledged that it was broken, but six weeks later no fix has yet arrived.
Same thing with battery reporting for zigbee devices.
So, again, I am glad that your system has worked well for you and I hope that continues. But it’s not simply a matter of customer knowledge and expertise.
Submitted with respect.
http://thingsthataresmart.wiki/index.php?title=Bug:_First_Reports