The RF 24mm f/1.8 that you mentioned: good plastics, lovely dimensions, okay-ish lead-screw STM, proper lens hood attachment, but then focuses externally and has a long focus range due to its macro abilities. Yeah, that puts me off, forget it, it's long gone.
Then the RF 35mm f/1.8: again, good plastics, lovely dimensions, but an old gear type STM that is noisy and jerky, weird lens hood, external focus, long focus range due to its macro abilities. Nah, forget it, it's gone and never to be missed.
The RF 16mm: okay-ish plastics, lovely dimensions, proper lens hood attachment, then again the old gear type STM that is noisy and jerky, and external focus. At least this one doesn't have to move its elements a lot - that helps. I tolerate it, but I'm waiting for a silver ring upgrade.
The RF 28mm: plastics are okay, dimensions are okay (not much to grab, really), its gear type STM seems a little better but not amazing, then external focus, and a weird lens hood. Similarly to the 16mm, this one doesn't have to move its elements a lot. Yeah, I tolerate it, and it's one of my favourite focal lengths, but I'm waiting for a silver ring upgrade.
The RF 50mm f/1.8 at least is cheap. Okay-ish plastics, lovely dimensions, proper lens hood attachment, then again the old gear type STM that is noisy and jerky, external focus, somewhat long focus range due to its good magnification, and pretty bad colour if you don't use auto white balance. For the price, however, I won't complain, as it is an overall better package than some of its predecessors. I'm delaying selling it because it's cheap and small, but I doubt I'll keep it.