You know, there will always be people who want to make money off of other people's creativity. I feel the same way about agencies as I do certification - pppffffttthhh!
This is my personal opinion, and it's ok to agree to disagree with me, I think a lot of people are making money telling VA's what they should and shouldn't do, and what their practice should look like, instead of VA's making money by doing their thing (or thang if you've got a twang

)
The potential of getting completely overwhelmed, instead of booking one project, one client at a time until you're as booked as you want to be, is there until you are completely sold on your own skills and value.
I have been doing this for almost 6 years now - some very prosperous times, and some very lean times. I was back at zero clients in March and April, and now have rebounded and have plenty of work...there's still room for project work here and there, but not a regular client without some serious juggling. It's new clients that friends referred, and a former client that I actually charge more now than I did before March. My business may not look like what you want, I work on site for a client twice a week, something I would never have considered when my daughter was an infant and I started out.
This is a completely doable business - you just have to decide what you want your business to look like

Don't get too hung up on how other people think the industry or your business ought to be.