I wonder if this is the real objection, or really just a proxy one? As in, yes, the new thing will compete directly with the old thing, but it will easily bring in way more than it "cannibalizes". So the company will likely come ahead. However, the old thing and new thing are likely developed by distinct teams, in different business units of the company. So I imagine this question is really a proxy for the old thing team asking, "will it cannibalize our currenet jobs?". If the answer is yes, it's not surprising they'll resist.