Of course it's a bad idea. Except for in very select areas, no fault evictions just don't really happen. Sure, a section 21 might be used as it's more of a fail safe than the others, but in reality people are evicted because they're not paying rent, they're causing problems with the neighbours or they're not looking after the property.
If a landlord has a property to rent out now, and there are dozens of applicants (because there's now a shortage), do you think those without a guarantor, with a pet, with not great credit, with kids even, stand a chance? It's all well and good saying they can't discriminate, but in reality, they pick the best candidate for them. If the stakes are raised by not being able to evict someone for even longer, when you know you're not going to get the rent arrears back, why would you bother?
Rents ARE going to go up.
Rental properties are going to be harder to find.
Landlords are going to be pickier with tenants.
Properties will be sold, but no the market won't crash, don't be stupid. A 5-10% drop in the market won't touch the sides at making it affordable for people.
The majority of people who rent still won't be able to afford to buy.
Homelessness will increase.
And guess what could have solved this? The government investing in social housing before they make a lot of landlords want to leave.