It's not an excuse at all. The exhaustion is real, and yeah, it absolutely can make depression worse because you're basically stacking two problems on top of each other. When you're already dealing with depression, your brain's already running low on resources - you're using more energy just to regulate your mood. Then pile on 6-7 hours of Zoom and you're draining what little emotional buffer you had left. The stuff about eye contact simulation and that weird delay in conversations, that's all legit, but there's also something people don't talk about as much: the constant low-level performance aspect. Even in a casual meeting, part of your brain is monitoring how you look, your background, whether you're nodding enough. That's cognitively taxing in a way an in-person conversation isn't.
The practical thing I'd try that doesn't get mentioned much - disable your self-view during calls. Sounds stupid but seriously, just hide yourself. Most video software lets you do this. It cuts out like 30% of the mental load because you stop unconsciously critiquing yourself the whole time. Also, if you can swing it, push back on the number of cams-on calls. Not all meetings need video; some can genuinely be audio-only or even async if people are cool about it. Worth having that conversation with your manager if possible.
The depression piece is the bigger thing though. If your symptoms are getting heavier, the fatigue might be a symptom or trigger, but it's not the root. Talk to someone if you haven't already - therapist, doctor, whoever. The Zoom exhaustion is manageable once you know what's actually going on with your mental health. Don't let it become a reason to avoid getting help.