https://moltin.com/ are a YC company who have raised a couple of rounds to do ecommerce in an interesting way, so clearly someone thinks there's a market for new SaaS platforms in that space.
(I have no affiliation, but I've met them and they're nice guys.)
They basically offer you a backend and a set of APIs to create your store. It's a great tool to use if you want to be in control of your store behaviour. On the other hand it requires you to have some technical knowledge.
(I have no affiliation, but I've met them and they're nice guys.)