Of course the Gemorah only applies to legitimate purposes. If it is an unessential purpose than of course the issur of seeing immodesty remains. You can’t do an issur because you want to go somewhere for pleasure. This is a davar pashut.
Furthermore, indeed, if one’s job involves issurim and he can get an equivalent job that avoids those issurim, he would surely be required to change jobs. Same if he could use another doctor who is just as good as the first that requires being oiver issurim.
No one has the halachic right to watch a certain movie because, as you put it, “that is what he wants to watch, then there is no other movie like that, then he has no other path.” That is completely absurd. You’re squeezing heterim that don’t exist due to crude desire.