It's interesting you call these sites and advertising opportunities absolutely necessary for things like visual arts businesses and yet don't think they are doing any good in the world. If the ad spots and targeting didn't exist then niche internet-ads-dependent businesses also would not.

Advertising is necessary for many businesses. The way Meta & Google sell ads and show them to users by algorithmically monetizing human attention is incredibly harmful to society & humanity. Meta & Google have been so successful at their business and at manipulating governments to avoid regulations and anti-trust enforcement that they have effectively put all other methods of advertising out of business. So, the only way for businesses to advertise now is to participate in the incredibly harmful world of online advertising as run by Meta & Google.