Wrong. 'Professionals' are worse because they have the money to turn any complaints into a long-drawn out legal battle. They can pay the few that win but the majority of tenants won't have the money to even start. Furthermore, if one company owns, say the majority of property in an area tenants even with valid complaints can be blacklisted.
Also, what exactly is the government going to do if a company is deemed a 'bad landlord'?
The company owns the houses. The government can't take over their management (if they even WANTED to they'd build social housing, no need for all this private landlording in the first place).
As I said the property, tenantless is still an asset so worst case the company can just kick the tenants out and leave it empty. Where do you expect them to go?
'Rules and laws' are only valid insofar as the resources available to defend them. So many naïve people happily bleating on about rules do you know how much going to court costs? How much time, effort paperwork etc even dealing ombudsmans requires (and how they're usually powerless anyway just telling you to taking it up legally?)
I lived in a flat with mould-covered ceiling for a year, currently my mates are living in a London flat with no hot water. Hasn't been for 6 months. Owned by a company, it still hasn't been fixed despite months of complaints, escalation, etc.
What rules do you propose that can make this better exactly. And how would they keep big companies in check better over small private LL's.