And this is where those protections I mentioned come into play.

I agree, but the reality is that most of those protections aren't very effective given the imbalance in power between a landlord and their tenant. "I can make your life hell if you dare enforce the protections against me" is a very common (usually implied) threat in countries with strong tentant protections.

However it does need to be profitable for people to want to make that investment in the first place.

Sure, there needs to be money in it. Property management is not a poorly paid job in most situations. And landlords can have a tidy profit for the hours they put in.

But the problem is that in most cases it goes beyond that, and in many even to the point where the entire mortgage on the property is paid off by the tenant which is just ridiculous.

At the end of the day, no amount of tentant protections is going to fix the problem that there is a housing shortage, and the homeowners and landlords are effectively a really broad oligopoly aggressively trying to stop anything that hurts their property values.