I've created a lot of Strikingly sites for small businesses and nonprofits, but recently one of my clients had a requirement for their website to be accessible to people with visual disabilities.
They loved how simple and easy to use Strikingly was, but unfortunately couldn't go with it because of the requirement.
A lot of nonprofits run into this issue.
I was playing around with the Wave extension, and it seems like it might be fairly simple for the Strikingly team to make some improvements.
For example, one of the alerts was an "orphaned label" in the contact form (i.e. the "for" attribute was not set, so a blind person wouldn't know which field the "Name" label went with).
I bet this would help attract more customers, because Strikingly is really great for non-tech-savvy organizations, which nonprofits usually are.