I wish everybody on the planet had the same couple of ovens too. Then your recipe for preparing cookies or whatever will have one big variable removed.
But because we don't have that, we waste time and energy pre-heating the oven, just to be sure that we're all cooking at the same temperature. And even then, ovens will vary in how they control temperature and grrrrr.
Same for soft/hard boiling eggs: the only error-proof way is to boil your water first and stick eggs in there for X minutes and then drench them in cold water. But that's a huge waste of the heat in the heating process. If we all used the same amount of water on top of the same heating source in the same place, we could use that pre-heating process as a part of cooking.
The original was good, but the version I got later has issues. Like sone of the button controls stopped working, and the pressure seal leaked and sputtered even when it was “locked” in the close position.
They didn’t say they were cooking the same thing every day.
I use the pressure cooker function of mine probably 4-5 times a week. Risotto, stew, chicken stock, tomato sauce for pasta, etc.
I eat a (large) breakfast of 1/2 cup dry oats, 3/4 cup whole milk, 1/2 cup water, cooked for 10 minutes at pressure, with a bit of brown sugar and any of dried cherries, raspberries, blueberries.
The massive advantage of an instant pot is if you cook w/ milk on a stove top, it requires constant attention to not burn the milk and have the burnt milk weld itself to the pot. Whereas in my instant pot, I throw the ingredients in with my first cup of coffee and come back in 30-40 minutes for hot breakfast and coffee #2.
Also, it makes a pretty good (not great, but I have a tiny kitchen, so I have to cut somewhere) rice cooker. Recipe: wash rice, drain, add same amount of dry rice and water by volume, pressure cook for 4 minutes. Depending on the type of rice, 3 minutes may be better. After cycle finishes, let depessurize on its own for 10 minutes, then open. Mix with a fork.
When they launched, they made an Instant Pots, and it was a fairly good product, with good marketing. There were other pressure cookers before, but this was beyond easy to use -- and super Instagram and Facebook friendly to share cooking videos.
But then they expanded out to... Air Fryers, Coffee Makers, even Air Purifiers... and it's just too much. They weren't going up against old pressure cookers that hadn't really been updated in 40 years, they were going up against established modern brands like Nestle and Keurig, and whoever else.
And they never really established a reason for all the different devices to live under that brand... and probably lost quality control (as you said). And yeah, I mean... I got an Instant Pots as a housewarming gift in 2010, and I loved it. So I gave Instant Pots to a bunch of friends as housewarming gifts... and it never seemed like a hit with the people who received it. At one point someone told me, "Thanks, but I already have one..." So I figured I'd replace my old one, and holy hell the quality in like 2017 or so was not good.
Like you pointed out the measurements on the sides were not accurate. And every dish I had made in the old Instant Pot didn't cook right in the new one. (Probably because the temps were off.) I was an idiot and tossed the old Instant Pot I had before really trying the new one out... then when the new one sucked I stopped using it all together and never bought another one.
Edit... here's a pressure cooker from like 2004. It was such a pain to clean and no matter what I did it splattered steam and liquid all over when it was turned on. Instant Pot was so much easier to use than this thing was.
https://www.overstock.com/Home-Garden/Wolfgang-Puck-7.5-qt.-...