Buttondown is a very useful, powerful tool — but it's not meant to be a one-size-fits-all tool. My philosophy in building Buttondown is to focus on doing a few things really, really well instead of trying to do everything okay-ish .
This is often considered antithetical in an industry dominated by venture capital and "meteoric growth or bust" philosophies — which is why I'm fortunate enough for Buttondown to be bootstrapped and sustainably profitable.
Here's a list of some very broad things that Buttondown doesn't handle (and has no real plan on handling):
If you're an ultra-sophisticated newsletter pro, you might be familiar with the concept of automated sequences that are roughly of the shape "when a subscriber signs up, send them email A, then a day later send them email B, then after that if they clicked on email B send them email C", and so on.
This is powerful functionality that Buttondown doesn't offer (and may never offer, since I don't think the median Buttondown customer is particularly interested in it.) If you're looking to have these sorts of workflows, I'd recommend checking out ConvertKit, which allows you to deeply integrate automation into your emails.
Buttondown offers a web archive which keeps track of the emails you've sent and presents them in a clean, stylish manner. However, if you're interested in more advanced publishing tools like block-based editing, WYSIWYG, and deep customization — Buttondown may not be the best tool for you. I'd recommend checking out Ghost, which offers newsletter & paid subscription functionality on top of their core CMS.
I love open source! But Buttondown is not open source software (though I have some aspirations for it to be.) If you want to use software that you can host yourself and audit the source code, I'd recommend checking out Listmonk. (Honorable mention goes to Sendy, which is self-hosted but requires a pretty reasonable up-front cost.)
Buttondown allows you to attach files, images, and that sort of thing to your emails (and to your concomitant web archives), but that's not quite the same thing as being a full-fledged media host. If you're looking for a place to grow your media presence by gating certain podcast episodes or comics, I'd recommend checking out Patreon or Memberful.
If you're looking for an email solution for your E-commerce store, it's almost certainly a better idea for you to choose an option that's deeply integrated with your store so you can handle things like coupon codes, shopping cart integrations, and so on. Mailchimp really shines here.
If you're not sure whether or not your use case is a good fit for Buttondown, please email me; I'm happy to chat with you, and I promise I'll spare you the hard sell — I care more about you finding the right tool than the tool being Buttondown.