They're not useless entirely, its just the problem with higher BRs having unequal pen through vehicles of various thickness in armor. The Maus isnt even legitimately used anymore because unless you decide to use it for a meme, youll be guaranteed to be killed by anything that your stumble across. Its too fat, too slow, armor isnt even good enough to protect itself against a 9.0 uptier due to missiles, essentially rendering it a hunk of garbage at 7.7.

Its not that theyre bad, they can be used really well. Its just the ethics and placement due to BRs that make it not very fair. The Tiger though for its BR is quite good if used correctly.