Too much custom stuff too quickly, there is a lot of efficiency in vertical integration and a fully cohesive stack but it takes a very long time to stabilize if you take that route.

We spent months trying to convince them of problems with their H2 implementation in their LB/proxy (they insisted nginx was at fault, spoiler - it wasn't) but had to leave (we also went to CF, which has its own problems). Eventually one of their employees wrong a long blog post about H2 that made it obvious they finally found and fixed those problems but months too late for my employer at the time.

It would have been infinitely better for us if they could have just fixed their stability problems, that abstraction suited us as did their LB/proxy impl and SNI pricing.

I wish them well, some really smart folk over there but I can imagine these reliability problems are probably really grinding down morale.