When I give this advice it usually means I don't think the output is better than the existing thing and the dependency cost is better paid in the form of integration.I probably don't think you'll really maintain your creation or think about others using it when you do.
As long as we are throwing shitty incentives around.
But on a more neutral note, it's a tradeoff with many moving parts. Different choices for different scenarios.
It's always internet strangers who are too dogmatic even though there's zero context.
People might add a redundant or dangerous library because they don’t know better but they don’t fight for it, like here.