It does the opposite. It opens one gate to funnel an attack through. An attack you can see for months down the line and prepare for. Right now, we do not know where any attack might come from. We can keep handwaving away competing projects up until one kicks us in the nuts, or some internal error or consiete undoes BTC. RGB is great for example, but it is playing catch up with all the proof of concept and market/brain/money theft Eth has taken away in the interim. Drivechain allows us to experiment with any new proposal, keep core safe and say to any other project "we can do that,but better". it is a moat around bitcoin that allows a strategic drawbridge