That's ignoring the specific use case of TFA though, which is not "I'm setting out to build something for my bigcorp to scale infinitely" but "I built a little tool that ended up handling more than I thought it would, good thing I used an ORM so that I could switch to X based on actual metrics and A/B tests."

I'm as anti-ORM as the next jaded dev but this is a picture-perfect use case for it: use an ORM to rapidly prototype and get the job done and leave a path for an industrial solution. The adage "you never switch your RDBMS" does not apply here.