I do partially agree with this statement Luke because it is highly evident in (please keep in mind I'm no professional and I'm a college student studying music) Mozart's clarinet concerto - the final movement - were yes there are parts were the music is written to include motifs and beauty but, there are also highly technical aspects towards the movement which include insanely high jumps for a reed player and very fast and decorative runs which as is know were written mainly for the virtuoso Anton Stadler and I'm highly confident that this was specifically done for the virtuoso and the audience who could enjoy the performers great skill.
Overall, I believe that music - at the time - was highly influence by the audience to which the music was to be played to and not solely based around specific motifs the composers came up with at another time - although they will have been modified yes. Obviously excluding Beethoven who was in his own sense special.