It’s also not as lucrative as most would think. I have a few rentals and it’s certainly not enough to quit my day job in IT. It’s maybe an extra $15-20k in my pocket at the end of the year after expenses and taxes and such, and I spend at least 10-20 hours a week doing accounting, maintenance tasks, coordinating contractors, legal stuff, etc. Sure, the equity is nice too, but it doesn’t do a whole lot for me until retirement age.
As far as whether landlords can be “good”, I see myself as providing a valuable service to those who cannot or don’t want to become homeowners. In a perfect world, those who cannot but want to become homeowners should, but the cost of housing has little to do with rentals and almost everything to do with zoning, development restrictions, and tax structure. Until that world exists, someone has to offer rental properties to these people, otherwise where would they live?