Pitch Controllers

How is it that commercially available automatic pitch controllers / angle keepers like the ones from Microgyros, Engel, Nautilus Drydocks, are the size of a postage stamp if not, slightly bigger while if you decide to build one yourself using an MPU6050 accelerometer chip and an Arduino you get something you'll have trouble cramming into say a 2" diameter WTC.

All of the APCs on the market were designed before Arduinos. Why are they smaller?
Would it be possible to use the MPU6050 only and couple it directly to the servo?

Arduino PCBs are general purpose controllers with a lot of components that are unnecessary for a single-purpose pitch controller, hence the larger size.

You might want to investigate something like this if you prefer to reinvent the wheel: https://www.adafruit.com/product/1500?gclid=EAIaIQobChMI4NPL2Nf68wIViIzICh0Ecg2MEAQYAyABEgIVRfD_BwE

if you really want to go small you can build your own gold wire bonding machine, a bit like a 3-d printer but uses fine gold wire and pressure (via a knife edge), the company I once worked at made one, but you do need a clean room and a supply of the bare chips (no resin package so just bare silicon die) then you simply wire bond multiple dies onto a very small PCB probably made from alumina ceramic.....
OK if your making many, but probably 100's rather than 1000's actually once you have the kit :)
seriously what you could try is rather than have a single PCB, use multiple smaller PCBs that are then stacked on top of each other, a bit like the arduino shield type of idea, but much smaller. You'd probably need to go BGA (ball grid array) package so another level of soldering as you have to use an oven (or hot air) rather than a soldering iron. You'd end up with more of a cube, but it would probably make better use of the available volume but heat transfer is a pig so put the high power devices on the outside....

Actually, thinking out loud, if you put all your electronics on a flexible PCB (more common nowadays) you could simply roll it up and push into the WTC .... sorted.
Quick animation:
https://resources.pcb.cadence.com/blog/2020-designing-a-flex-pcb-prototype-pcb-design-tips-and-considerations

As mentioned, with high enough volumes you can get the chip functionality you need and no more, in the smallest package and use the latest manufacturing techniques not available to us. You don;t need to have the latest stuff yourself now, you use a contract manufacturer who has and can spread the cost and knwos how to use it.