Again, Foden can in fact play on the left. It's not ideal and within England's setup doesn't get the best out of him, but he can do it. If he really doesn't want to drop him, just have him stay wide. Or swap him and Bellingham around. Bellingham can also play on the left. Again, far from ideal, but a possibility
As for Gallagher....honestly, I can kind of see the rationale - the team lacks fitness and energy, so throw in the guy who is fit and has boundless energy - except, well, it's just stupid. But then again it's a summer tournament, the other team is also knackered so one guy with boundless energy really might make a difference...we'll see I guess
I get that for England fans that is depressing though. Bracket is breaking out in such a way that the team might make the final even with Southgate's fumbling, and then it's just one game, a bit of luck and they could win. But yeah, going out without trying any of the more obvious tweaks(Gordon/Watkins on the left, Mainoo/Wharton in midfield, Palmer) would be depressing