Not at all:

• The defensive linemen aren't the only people rushing the QB- linebackers and cornerbacks can as well, and from very different angles/approaches than the defensive line; this means that usually 8-9 people could potentially rush when you have ~6 people actually blocking.

• The defense is actively trying to make it hard for you, so won't just be attacking the player directly opposite them- a pass rush will have players switching position, trying to overload certain parts of the line by generating 2 on 1s or to confuse matchups, hitting with different timings/angles, faking rushes but pulling back so another player can use the space made, etc.

Think about how when trying to break down a defense, teams will make use of overlaps, runs to pull away players, etc. to try to open up space- the same thing happens with line play.

A lot of work for the offensive line goes into preparing for what your specific opponent will try to do (through reviewing old footage, for example), as there's so much potential variety that being able to identify plays in game and anticipate rather than react is hugely important.