It's never a waste of time to submit a proposal if you can be sure it's going to stand out from the crowd. In your case, the crowd is very large. I just did a search for 'virtual assistant' and then filtered for native/bilingual level English, hourly rate $10-30, earned at least $1 on the platform and active within the last month. It turned up 1,406 FLs.
Figure out your strengths, what makes it worthwhile for a client to hire you over anyone else. Search UW for people doing the work you want to do, earning what you want to earn, and see how they are qualified, how they are presenting themselves, etc.
Good luck!
