Einstein gets the hero worship mostly because of the Annus mirabilis papers on the photoelectric effect, Brownian motion, and Special Relativity. General Relativity was more a curiosity of sorts until the 1970s, and even today people connecting astrophysical observations with Einstein gravitation tend to work with a (often linearized) approximation for practical reasons and with a range of theoretical justifications and mechanisms to connect back to the Einstein Field Equations as the underlying more-fundamental theory.
Practically every grad student encountering Kaluza-Klein (and other supergravities) or the PPN formalism will spend some time with Nordström's gravitation (and of course it is discussed in §27.6 and §38.2 of Misner Thorne & Wheeler, the gold standard textbook). In the latter case it is straightforward to see in modern terms where Nordström's 1913 theory would clash with solar-system observations (it was ruled out by the Eddington eclipse observation) and spectacularly falls apart for compact massive objects like the Hulse-Taylor binary. The theory inverts the spatial curvature generated by matter (PPN \gamma parameters for Newton, GR, and Nordstöm 1913 are 0, 1, and -1 respectively) and is only half-right for gravitational nonlinearity (\beta parameters 0, 1, and 1/2). Einstein-Fokker 1914 fails under PPN analysis in the same way, except that they properly fix the \zeta_{4} dynamical conservation parameter as 0, unlike Nordström 1913.
In my view, early 20th century alternatives to GR are interesting for how they failed. I accept the part of your argument that it is more interesting to some than to others about how much cross-fertilization there was among the developers of these theories. However, only GR has survived contact with all experimental tests, and it has proven extremely difficult for alternatives to match over multiple solid angle and wavelength scales what astronomers observe. The ways in which various extra-field approaches have failed are frankly more useful for theoretical physicists than the ways in which they were developed in the first place. And for astrophysicists, the only thing that matters is what has not -- so far -- failed.
So however he got there, at least with respect to gravitation Einstein deserves recognition for having produced pretty much the only viable physical theory. There's really only Jordan/Brans-Dicke in the limit of a vanishing \frac{1}{\omega} parameter, but at zero the theory reduces to GR itself; Einstein-Cartan-Sciama-Kibble if one does headstands to suppress spacetime torsion; early-decay bimetric theories, where the second metric field decouples or vanishes before nucleosynthesis; supergravity, if one figures out how to hide the gravitino; and string theory (M-theory), if one figures out the landscape problem and/or works out a general emergence of a PPN match. Notably every one of these evolved from General Relativity mostly because of its unique successes -- however, I think it is more interesting and better to say that these remain viable because they can in certain circumstances fully reproduce General Relativity.