Other than the fact Oilers PK hasn't been good this year and Brown has missed out on a lot of SH scoring chances.
Brown also has the worst +/- on the team meaning he IS getting scored on as 4th liner.
Being outscored (more or less +/-) is not the same as "getting scored on".
Brown has a 1.9 on ice Goals Against / 60 which is at or near the lowest on the team (with his common line mates Ryan and Holloway right there with him). In contrast, McDavid (2.9), Nuge (2.8), Draisaitl (2.5) are all about a goal/game higher. The difference of course is that unlike Brown/Ryan/Holloway, they can outscore their deficiencies.
Brown can't do much... but if you need a shift or two of low event hockey, he can be put out there to keep the puck out of our net. Not every "role player" is going to have a balanced skill set... sometimes you need a gamebreaking risk taker, other times you need a glass-and-out guy or "get pucks deep" kinda guy.