Schools are structured to benefit girls, and the deck is absolutely stacked against boys. The vast majority of teachers are female, and they mark boys worse for equivalent work. [1] Boys generally require more physical activity than girls, yet the majority of school is "sit down and stare at this whiteboard".
Of course they're less motivated, it's quite literally a rigged game.
I think you're oversimplifying what is a massive systemic issue into two points that, while true, might not contribute as large of an impact as you're assuming.
Also, just in defence of female teachers, I don't think it matters so much that they're women, but that they understand that boys will be boys. Anti-male teachers were, at least in the experience of myself and a friend who went to a different school (we discussed this once), definitely present but firmly in the minority.
Of course they're less motivated, it's quite literally a rigged game.
[1] https://www.bbc.com/news/education-31751672