I'm really surprised to hear that. ST has always been one of my favorite manufacturers. I find their datasheets to be clear and well laid out, though I will note that I'm usually more interested in the hardware side than the software side. Their chips and boards are also high quality and convenient, e.g. GPIOs are often five-volt tolerant, Nucleo boards come with well-made breakout headers and several peripherals (at seemingly impossibly low cost), chips have wide supply voltages, etc. I can't say I know anything about their errata (I've never run into any), but even if the situation is as bad as you say, that's quite a harsh condemnation, especially considering how widely-used and successful they are in industry. Do you have other complaints?

I’ve used their accelerometer (LIS2D). Performance and specs are great - it was just a pain to develop the embedded interface with it because the documentation had a bunch of mistatements and was missing critical information (a weak pullup on a certain line caused a bunch of current consumption - took days to figure out). Also they had an off by one bug in their LIFO queue that took a long time to figure out. Once you getting it working its great. Last time I checked they still hadnt updated their documentation with what I reported to them...

can confirm. found multiple issues around SDRAM interface in STM32f429, only some are in the errata doc

Which MCU makers do you prefer?

Atmel (now under Microchip). They have great documentation and software libraries. And they actually acknowledge hardware errata in the documentation.

Yeah I love those. They highlight features xyz on first page of datasheet. Then on the last few pages its like btw features xyz dont work on rev A-F. And your supplier doesnt know what revs they have...

I used a SAMD21 for my latest project and I was definitely impressed with it versus STM32s.

I will say that STM has definitely released better tools that make it much easier to get designs up and running (STM32Cube specifically).