Can you? The same Glitch that shut down last year? https://blog.glitch.com/post/goodbye-glitch
Regardless, ActivityPub and ATProto have different designs and goals. Your question is akin to comparing a helicopter and an airplane.
There's no such thing as a "ATProto server". How complicated it is, and the trade-offs it made are valid criticisms of it. It all depends on what exactly your goal is as a participant of a distributed social network.
If the thing you want to own is your identity and data, you can fairly easy run a PDS yourself. If the thing you care about is different moderation decisions, you can run your own labeller (moderation system) or subscribe to another someone else has made.
To 'own your data' you just need a PDS, which should be cheaper to run than an ActivityPub server
To build an app you need some of the more expensive parts
Honestly my main question here is "If you disagree with various ActivityPub instances' defederations, you can get around this by starting your own instance that federates with everything; is there an equivalent for bypassing Bluesky's moderation decisions?"
Want your own AppView so you can have nekusar.net and post your messages and people on BSky see it ? https://github.com/blacksky-algorithms/atproto
ActivityPub zealots would do well to calm down for one second, this can't be good for your heart man.
If you just want to post messages on your website that get syndicated to BlueSky (as blog post links or full threads or whatever) you could have your website server make API calls to your PDS (whether that's self-hosted or not).
If you're talking about building your own custom BlueSky app, "AppView" is not synonymous with "viewer app"; basically it's an "AppView" because it provides a "view" of the network necessary to power an end user "app". I.e. it holds a copy of every single post, repost, and like, so you don't have to. Your custom app would simply make requests to the logged-in user's PDS, which routes most of those requests to that user's preferred AppView.