As an ex immortal I can tell you that the real and true problem with insta-lockers is not that they make it harder to make a sensible team composition. Neither is it that they choose to play what they are good at or prefer, that is understandable to an extent. The reason insta-locking is getting a lot of flack is because the people that do insta-lock are more likely to be people with huge egos, that don't communicate, that are toxic or that ragequeue. It is not as much the insta-locking itself, as it is the negative reputation that comes with the people that do insta-lock.

If someone communicates with the team, does acceptable and is good at their role, I think most people would not be left with a sour anger for insta-lockers after the game is done and it would not have such a bad reputation.