I completely agree with that. But as of now, keep in mind there are no professional Lemmy or Mastodon instances that generate money by advertisement AFAIK. Which means it’s all donations and volunteering.
So if Lemmurs/Lemmonians (what do you call a Lemmy user?) start uploading large amounts of data, that will cost bandwith and server space.
But you’re also right that Lemmy needs content to become attractive. My comment was mostly a warning or heads up.