Long and f/2.8 gets heavy and expensive real quick. A 300mm f/4 prime (perhaps with a TC) is about the sweet spot of reach and affordability plus still easily hand-holdable. That said I keep toying with the idea of a 300mm f/2.8. Maybe one day I'll take the plunge.
Some great photos though. Proof you don't need overly fancy gear for most shots.
While I believe you're right and I've tested the *60-250mm F4 lens, the shots above were mostly F4 - F4.5 and it's just the shutter speed that gets way too slow to handle the IQ properly. If I could have gotten twice as fast shutter speeds at F2.8, many of the throwaway shots could have been used.
Downsizing to a more moderation resolution with a soft resizing filter should solve that.
Computational photography does wonders without having to think. I compared edited shots from a single still on my system camera to an iPhone auto-HDR shot and the results were surprisingly similar, though I still had better balanced the wide dynamic range of the shot.