The problem is the support matrix which is crazy in this area. I think ServiceNow did pretty well without having too many adapters (of course now they have quite a few - https://docs.servicenow.com/bundle/orlando-it-operations-man...). So if the product is easy to use, reasonably priced, and has the ability to schedule data imports, why not?
Thanks for your valuable feedback! Yes, you're right. But for now I choose to make the product exceptionally easy and flexible (even with manual data entry). Automation can be added later, after concept is validated.
If you’re thinking manual data entry will be the primary use case for an asset control /CMDB, you will lose badly in the marketplace.