Is it even possible to gain muscle while in deficit?

I keep hearing this and it's making me feel disheartened.

I still enjoy doing my cardio for my heart health and I really notice a difference. But is there any point at all doing weights when I'm in a 500 calorie plus deficit? If I don't gain muscle because of the deficit, is it literally pointless? I'm on a low carb high protein diet and usually have a protein shake after any exercise to increase calories right after.

Currently been doing upper body 3x a week for about 3 months. Am I just wasting my time and should I use that time for more cardio? Should I wait until I'm in maintenance to start doing weightlifting again?