Yeah, a bunch of people posting negative stuff on Twitter is probably SOP for the different freelance websites. It is easy to create something that can spam a bunch of 'lifelike' complaints.
I am not sure how it is 'easy' to get rid of scammers.
I would point out that my 'promotion as compensation' is the only 'easy' solution to dealing with scammers.
Consider:
I make a new account.
Fiverr reaches out to me with a job. (Note that the conditions for what they look for aren't transparent. So it isn't easy for scammers to figure out the conditions)
They offer me a job. I do the job. If they like the job, they do a free promotional gig for me.
I think that the issue is that you are too used to being on Fiverr. I am a newbie and no one really knows if I am 'real' person or a scammer. I have clients that pay me very well to edit their books, but because that is all word of mouth it doesn't help me use a job board to find new clients. I get seven gigs on Fiverr. Every client that has hired me has liked the results, but it is always small fry offers.
Honestly, I would rather do ten 'free' gigs to earn some credibility real fast than to be forced to negotiate 5-20 dollar.
This applies to other sites and not just Fiverr, there is absolutely nothing more annoying that putting up with someone who is trying to negotiate me from 20 dollars to 19 dollars. I have better things to do than argue over pocket change.