While I agreee with you in a general sense p f, IMO there is value in the old lenses. Satisfaction is getting decent photos and the better ones are capable of that. Wildlife photography especially is opportunistic and if you don't have a lens then you don't get a pic. Plus you get on the learning curve. The trick is an informed choice of vintage lens. And I am not surprised if there is disappointment with this or that x-300mm AF consumer zoom, quite frankly most of these
are a bit of a waste of time at 300mm, being slow and sub-par resolution, (the pentax FA 100-300mm I acquired a few months ago for next to nothing was a surprise exception, see my pics in the 300mm thread and the FA unlimited thread). Value, in the end, is in the eye of the beholder.
With telephotos, you pay exponentially more for incremental improvements in IQ.
Tamron "nestar" 400mm f6.9 @ f11. IMO the best of the real old 1960's vintage t-mount preset 400's. This lens has the cachet of being the only non-mirror 400mm that you can fit in your pocket.