Is there such a thing? Sure, if you focus on the very ends of various spectra. There are times when there is a right bike: full suspension for high speed super chunky descents, a time trial bike for the state championship, a ‘cross bike if you’re trying to win at Gloucester.
Or if your mind wanders to if only’s and the imaginary ideal perfect machine, or the deflation and irritating obsessive agitation of simply misbelieving that you’re on the wrong bike. It’s actually very unlikely that you are. (On the other hand, Craig and I did come to the grudging conclusion that perhaps this loop was not appropriate for our local Tuesday night effete roadie group ride.)