I have an online shop to support my podcast on Tudor history. I originally set up my shop thinking I'd sell some fun leggings using print on demand vendors. And it's grown into a bit of a behemoth. Which is great! Here's the thing - lots of creators use Redbubble and Spreadshirt and other places like that, which is fine, but the difference is that when you do that, they handle the entire sales process. This is fine if you don't want to know your customers, but if you're running an online business, then being able to capture that sales information, and get mailing list sign ups, is crucial .
You can still use print on demand vendors, only this time you control the entire sales process. Everything is branded for your business. The tags in the leggings are branded for you. The mailing address is your company. It's all yours.
Of course, the downside is that you also have to handle the customer service questions that would normally go to the Zazzle equivalent. But if you are really wanting to build a business around your customers, you want that touch point. And you get to keep all the profits.
With all the apps, you can have a store that really expresses who you are, and lets you control the entire sales process.
I'm not a fan of how much is only included in the more expensive options, and how much is only available through paid apps. Of course it's great to have the options at all, but it's very easy to start to run up high bills. At one point I was paying close to $100/mo for all my various apps!
I also still use other marketplaces like Etsy because it's the distinction between selling at a church craft fair and setting up your own shop. At the church craft fair you're pretty much guaranteed some kind of traffic. With setting up on your own you have more control over the feel, and ownership of the shop, but it's up to you to go out and get all the traffic.