I've purchased plants countless times on either Etsy or eBay over the years. You can often find things no one else is selling. And you can review photos and feedback on sellers to see what kind of quality plants they sell, along with what the customers think about that particular buying experience. With a good seller who runs a professional business, they are both knowledgeable and reliable in terms of the quality of plants you can receive. However, unless you're willing to overlook some potential problems, it's best to avoid any poorly reviewed or otherwise suspicious sellers on these platforms.
I tend to cut people some slack when it comes to things like packaging, because they are often people on a budget trying to make extra money. They aren't a large business with printed specialty packaging. You might get your African violet cutting mailed to you in a pre-owned Amazon Prime box, wrapped in the local town newspaper. With three different kinds of packing peanuts. Also, many of these people have not gotten customer service training and don't have "scripts" about how to respond to feedback. But on the other hand, some sellers might surprise you with delightful thank you notes in their actual handwriting. That's something you rarely see from the larger plant sellers.
Btw, while I'm on the topic (sort of) of Amazon.com, it's usually a good idea to avoid buying on this platform. Though there are a few exceptions. For example, a few of the larger companies also have Amazon accounts. I've purchased Park Seed items from their Amazon account, and directly on their website. It's the same thing coming from the same place. There are just a lot of scammers selling plants on Amazon, and there is no good customer service to handle plant requests. Except the main Amazon customer service, and they don't know anything about why your plant arrived wilted. I generally just have a bad vibe when it comes to Amazon. That's why you often see a lot of plants or seeds with bad reviews. The nature of selling plants doesn't really lend itself well to the Amazon bulk listing feature.
Often you will find the same people are selling on Etsy and eBay. Some people, like me, will check both sites if I'm looking for something in particular. Other people will only check one or the other because they have an account with that specific platform.
I find the eBay search function is more accurate and doesn't fill the results with a lot of similar, but not exactly what you're looking for items. An Etsy search is more likely to bring up a lot of content that is somehow related, but not exact. Though you can still find things.
If a seller has been around for awhile and has very good feedback, the plants you receive are generally as good, or even better, than what you might find at a larger plant company, greenhouse or farm. For example, some of the best dahlia tubers I've gotten were on Etsy and eBay. For about the same price as the larger companies, you often get bigger, healthier and better tubers. That's not always the case, but it happens more often than you might think.
The thing about plant sellers on Etsy and eBay is that they are dealing with smaller amounts of plants, managed by usually one person or a family. They are more likely to know exactly what's happening with their garden or farm, and manage their inventory well because they are doing everything themselves. A farm with 20 workers has a lot more moving parts. But on Etsy and eBay, the person growing the plants, harvesting them, making cuttings, rooting the plants, advertising, listing, answering questions, packing and shipping, are often all the same person or in the same household.
You will still have to keep an eye on things like diseases and insects, just like a shipment arriving from a larger farm. But I've seen it happen, though not frequently, from both types of sellers.
When you're purchasing plants and you feel confident someone won't swoop in and grab it if you don't get it fast, you can "favorite" the item. You will often get an offer from the seller within a few days for a discount. The discount is generally around the cost of your taxes, which can save some money. So if you're on a budget and it's not an urgent purchase, that can save you a few dollars.
Another reason I sometimes end up on Etsy or eBay is that I want an item that is generally sold at a specific time of the year. But the major companies don't sell it all year long. They do this because it's less likely to grow successfully if you live in Minnesota and are buying say a dahlias tuber in August than the same tuber in April. If you know what you're doing and have a good reason to buy outside of the season, you can sometimes find those items on Etsy or eBay "off season." Just don't blame the seller if you're buying a garden rose in January, and something goes wrong. There are all kinds of reasons why someone might want to purchase a plant in the off season. For example, if you live in Florida, the best time to plant your tubers might be in the autumn, instead of the spring because of their hot summers and mild winters. So you'd find it very difficult to order tubers from the main farms because they simply won't have anything for sale in the autumn. But an Etsy seller could simply dig up a tuber on the spot, or send one from their inventory that's stockpiled for the winter.
Also, manage your expectation for the plants when they arrive. They will often be shellshocked from being shipping across the country over several days. They likely won't look as fresh as the photos for a few days or weeks after you receive and revive them.