Salesforce is a plague on every company it buys. They completely ruined Heroku and I expect it won't be long before Slack starts to suffer.
That's not to say it was then neglected by them later on!
Once K8s got wide adoption Heroku was over. Selling Heroku to IT was a huge pain in ass as the key decision makers mostly make résumé-driven buying and engineering decisions.
Did Salesforce neglect Heroku or allow it to operate independently? It’s a matter of point of view.
The reality is that Heroku saw itself more and more irrelevant vis à vis its competitor and without the funds to compete. It’s only hope for survival is to become more and more relevant to Salesforce customers while largely out-competed but the big 3 for everyone else.