Oooh, very close vote here.
I say blame the system rather than the people on the whole.
Obviously, do blame landlords who overcharge, overcrowd, take advantage and don't bother to look after rented accommodation, especially those who endanger lives.
Otherwise, when property is such a good investment, I can't massively blame people for putting their money into it if, say, they inherit enough to buy an extra place when they already have one, or somewhere to rent out when they don't want to be tied to an owned property to live in.
I think most landlords do want to do their best, many are clueless because you literally get no training nor any requirement to sign up to minimum standards of knowledge; some are well intentioned but farm out management to shitty agents who never pass on messages from tenants and make them look bad.
It should have never been allowed to get to the state whereby so many people rely on private landlords for housing. Most LLs who just own one or two properties can never be great LLs because at some point they will need to realise their investment. It's worth pointing out that most of these are not selling up to buy a Ferrari or fund a big holiday or some frivolous reason but to upsize their families home, or because they're retiring or divorcing, or giving the proceeds to their kids. This is not much comfort for tenants, but I do get a bit annoyed at the assumption sometimes that a LL is just selling up in order to throw their cash around.
Yes, I have been a LL, although I bought my house to live in and did for 4 years, but had to move out to live (then) HTB as his job was elsewhere.
In summary - the system is awful, but not all landlords are awful.