gp used "rent seeking" correctly.
The concept of "landlords do nothing while collecting passive income, therefore not creating any value but instead are just exploiting that they own the land" would be correctly described as "rent-seeking behavior".
You should read the wiki article.
Criticising landlords is fine, but words (and phrases) have actual meanings, and the term "rent seeking" has literally no place in a discussion about landlords.
This equally applies to any investment income wouldn't it? Dividend, loan interest would all be classed as "unearned income" by a certain economic theory I won't name that keeps causing people suffering a century later. Don't do that.