at what altitude do you claim the temperature is significantlty hotter than near sea level
For example at 60 ft altitude, on the apron of DXB airport... This is when your composite structure is above 60°C just when you perform a takreoff at MTOW.
Uhhh how many ' ALL black aluminum " aircraft are flying since the707 -321 you referenced?
Compare a composite glider with a metal glider, and then compare the 707-321 stabilizer with a 787 stabilizer. Still the same rib and stringer stiffened shell, connected by fasteners.
Yes, we learned our lessons about sandwich structure in rough commercial air transport environment. Yes, we had issues with bonded struchture. Yes, we need a design which is quick and easily repaired. And yes, some composite design today is really innovative (e.g. the CSeries/A220 wing produced with vaccum assisted RTM), or the wound barrel design of the 787 fuselage sections.
But a majority is still a metal design using composites material. We are still far from using the potential of those materials in an adapted design.
For example we use multiple load path design in metal structures for damage tolerance reasons. Composites material however is inherently damage tolerant, there are already millions of load paths (fibres) which fail individually, so the complete design concept could be completely different. We can embed structures health monitoring devices in composites layup (impossible in metal) to detect damage in service without the need for dedicated inspections. This also means we can design with significantly less access provisions.
There is still a lot of future ahead with respect to composites aircraft...
However, the hybrid 77X may tell whether it performs better in the end, compared with the all composites 787. There probably is a reason why Boeing did
not change the fuselage to carbon, maybe the same reason why the A350 fuselage design is completely different from the 787 fuselage design (panels vs. seamless barrels), and why Mitsubishi switched back the MRJ wing to aluminum.