It's not from people, it's from corporations that rent out 3000 or more apartments.
Fighting against these companies will only drive prices higher. It is stupid.
I've never met anyone who prefers Vonovia etc. to housing cooperatives, or failing those small private landlords.
My last rental with a big company was perfect: they even skipped asking me for rent deposit, my work contract was enough. Their maintenance team was full time dedicated to maintain the same buildings, so they knew perfectly how to repair everything, they were quick and diligent. They knew if they didn’t fix it right, they would have to do the work again.
Economies of scale is what allows these big companies to offer better prices and better service than private landlords.
It's great that your last landlord company treated you well! But that's not the experience most people in Germany have. For example, I personally know >10 individuals who rented from Vonovia and deeply regretted it, because there were so many issues that maintenance only covered up superficially while NEVER fixing the actual issue. Even for severe issues, they usually waited 3+ months before sending anyone out - in one case a wall showed obvious water damage & mold, and it took 4 months PLUS a letter from a lawyer before anyone followed up on their dozen reports!
> Economies of scale is what allows these big companies to offer better prices and better service than private landlords.
Sure, that's the theory. But when reality does not align with theory, something must be missing: your model only works as long as the market fulfills certain conditions, which the housing market in Germany (and likely most of the west) does not fulfill. If you haven't heard of these assumptions, I'd recommend looking into non-fungible & inelastic markets.
Because previous attempts at discussing such topics were usually met with hostility, I'll only go into more detail if you can bring empirical counter-evidence, or if you were sincerely unaware of the limits I've mentioned.