Nice post! Unfortunately, the Competition in the Writing field is just overwhelming. There has been too much saturation, glut and over-supply in the last few years due to such low entry barriers. And now that COVID has forced most people to stick to their homes and search for "online jobs", writing is where most just flock to!
It'd be highly useful if you can prepare a table or infographic where for each of these writing platform, the test difficulty level, average pay, payment method and accepted nationalities is given. Many of these platforms don't usually hire from outside of US/EU countries sadly.