Well written article and welcome to the forum.
I tend to agree with you and have said as much back in January when he had hip surgery. I see three factors working against Andy:
1) The hip surgery itself. I'm no doctor, but my sense is that it will be difficult to return to his previous form given his physical style of play and lack of a major weapon, as you emphasized.
2) The resurgence of Novak to go along with Fedal. Andy Murray is the 4th greatest player of the last ten years and probably the best player of the Open Era with fewer than six Slams, and arguably as good as most of the 6-7 Slam lesser greats. But he's always been the 4th best of the group, and I would also add isn't noticeably better than Stanimal or del Potro at their best, and both are playing well. So the old guard isn't done and Andy's one year of dominance saw an injured Roger, a struggling Rafa, and Novak going AWOL. The point being, he might not have that window again, at least not before...
3) The rise of NextGen. The Holy Trinity are so much more talented than everyone else, even in their 30s. But at some point the young talent will rise as the old talent falls; this might be another year or two or even three, but eventually as the NextGen reaches their peak and the Holy Trinity are a couple years older they will be close enough to compete. But Andy's talent level isn't that much higher than what we can imagine to be the peaks of Zverev, Shapo, and Tsitsipas--all of whom seem like future multi-Slam winners, if not 6+ Slam greats.
So yeah. Combining those three factors and it would take a perfect storm for Andy to win another Slam. If I were to list active players by their likelihood of winning future Slams, I'd say:
Probably (say, better than 50%): Djokovic, Nadal, Zvevev, Tsitsipas, Shapovalov
Maybe, solid chance (less than 50% but not negligible): Federer, Cilic, Wawrinka, del Potro, Thiem
Unlikely, but there's a chance I suppose (negligible, say >20%): Murray, Dimitrov, Nishikori, Raonic, Goffin, Anderson, etc
Maybe someday, but hard to say (?): Tiafoe, Kyrgios, Rublev, Edmund, Coric, Khachanov, Moutet, Aliassime, etc
Not the best grouping of players to be amongst. But maybe I'm being too harsh on Andy?
:cuckoo: 
