I agree with you, such a bittersweet taste in the mouth.

I don't think that a Marketing company is the right type of company to run Postmark.

Postmark care about deliverability not about "engagement". Everything is about being sure your mail get to your clients not about how to craft marketing campaign from their product.

How much do you bet ActiveCampaign is going to add some email editor and campaign management feature to Postmark ?

I truly hope they won't touch their acquisition and let it run how it always has instead of adding feature that doesn't make sense with the product just to compete with MailChimp and other big names.