Looking at Japan, China and Korea, countries with falling birth rate and strict immigration policies, it seems that the expected higher wages and increased births never materialize. The remaining workers are just squeezed harder so the economy can continue to function and grow, what results in people having less children because they have to work so much, and it ends up in a downward spiral.
Once any site is big enough, marketing, trolls, influencers and propagandists move in too. Then it comes down to moderation to keep toxicity down.