We didn't get where we are today, in any field, using this approach. We don't have 30 different measurement systems, and a company whose job it is to coordinate conversions between them. We don't have 30 different text file encodings (any more!), and a company whose job it is to automatically convert them as necessary. We say: here's the standard, and now you can use it or be ostracized in the market.
If writing custom adapters to interface with GitHub/GitLab/Jira/... is anything other than a temporary solution, while you work on some grand plan to get issue-trackers all on the same page, then it's just a money-grab on the road to failure. Someone will cut off API access, or drive up your costs, or refuse to offer an API, and users will be stuck with "one command center (for the 3 most popular services they use), plus 3 oddballs", and it's just not going to be worth the hassle.
It's a band-aid. Normally you stick a band-aid on something that will heal itself, and then rip it off tomorrow. This particular problem is getting worse. This is a very pretty band-aid, but you've applied it to a sucking chest wound.
Gmail already reminds me of stuff like emails I didn't respond to. I've set up some filters and scripts to do more like create a triage queue for PRs and such.
It's also those "filters and scripts" you've set up to create your own triage queue that we're trying to replace. The average user should not have to write scripts to receive and process their work in an efficient manner. That's what we're trying to solve at Monolist!
Have you considered pricing by #integrations connected?
To be honest, just based on the screenshot it seems like a nicer management for even a single service than GitLab/GitHub's notifications.
The number of tools used daily is growing, which is in one way beneficial for the worker since they get a better and more specialized tool to do their work. However, it increases fragmentation and the chances of missed work.
Email is the most common solution, but that has its own downsides and seems to be used less and less for daily work. We think the solution is an ever-updating and fully synchronized “command center” for everything across every app you may be using.