Possibly because the overall market isn't nearly as big as it was (thanks in large part to phones with cameras), but I doubt the birder segment has shrunk, so it could be relatively a bigger chunk of the current market. We shall see. In the meantime, I really like my R7.
An interesting suggestion! I came close to getting an R7 more than once, it was a rare bargain in the lineup.
The R10 is also a very good value. I steered a neighbor to one and he loves it. Very compact, but quite capable, only missing IBIS, but not a big issue for those using APS-c lenses with IS. He has the 18-150, the 10-18, and the 100-400. Very lightweight kit with a 40:1 zoom range and all the lenses are quite sharp at 24 MP. Sensor has DR almost identical to the R7.
Yes, very long lenses can produce excellent results if you choose your conditions carefully. I have the RF 200-800, the RF 800 f/11, and the EF 800 f/5.6 L and use them all. My primary use is photographing hummingbirds, and that is close up work were atmospheric distortion is minimal. Long range shots require patience. Depending on where you live, the air can vary from never being clear to really good visibility about 30% of the time, so for clear distance shots, you need to be aware of "seeing conditions", as the astro folks call it, and be prepared when conditions are right. Note that 800mm on an R7 is equivalent to 1280 mm on an equivalent MP FF and very close to 1120 mm (i.e. a 1.4 extender) when comparing to an R5.
