Very few rentiers is likely true. However, very few landlords are rentiers. The average investor owns 2 rental units [1]. And the vast majority of property investors have full time jobs and mortgages on their rental properties (I can't link directly to a source, but Buildium regularly conducts surveys to understand property investors).

To paint landlords as rentiers who can easily afford to go without rent or with greatly reduced rent is wrong. It mischaracterizes the problem in a way that will lead to bad solutions.

If there is to be rent reductions or forgiveness, there must also be reductions, aid or forgiveness on mortgages, property taxes and utilities. Somebody needs to pay for these things. Yes, profits will be reduced, but losses cannot be sustained for as long as social distancing measures are expected to last.

[1] https://www.huduser.gov/portal/pdredge/pdr-edge-frm-asst-sec...