I'm not in the habit of accepting homework assignments from randos on forums, but:
Garmin bike head units went from rock solid and reliable to deeply sketchy and prone to losing sync, losing rides, and just flaking out around the same time (roughly the evolution from the x00 series of devices to the x10, e.g. 500 to 510, 800 to 810, etc). This was well documented in industry press, and a super common observation to make in the cycling groups I ride with.
Ten years ago, it was nearly a Garmin monoculture on the rides I'd do. One by one, my pals got pissed off about how flaky the devices were getting, and that led to a drastically reduced Garmin footprint.
Now, Wahoo has a demonstrably bigger presence, and Karoo/Hammerhead is creeping in, too. If Garmin had kept their quality up, that wouldn't have happened. GPS tech was theirs to lose.
Long time Garmin user here
Have not noticed a drop j on n software quality.
What specific metrics would you put forward to back up your assertion?
As the saying goes extraordinary claims require extraordinary evidence.