This is probably just a lack of familiarity with the playbook for selling B2B. People that have been doing it a long time can intuitively navigate around these obvious objections.

Outside of some rare cases, there are standard positioning techniques to avoid being evaluated for completeness relative to whatever the business has. For example, not positioning your product as a replacement for existing products -- "and" not "or" -- is an effective approach. Trying to be a feature for feature clone of an existing product they already use is a losing proposition, so having a strategy to reframe the discussion away from that perspective is a requirement.