Here is something I witnessed just last week (and I'm neither a scientist, nor qualified; I just believe face masks are ineffective - judgement based on statistics, reports read, media items, etc, etc - same as we all use to base our own judgements on).
I'm a bird watcher and last week, our bird watching group visited a nature reserve. It was a bitterly cold day. We went in a bird hide and watched the birds through the windows. I stood behind a woman and got distracted by the swirls of what looked like smoke coming from her face area. At first, I thought she must be smoking, but then realised she wasn't. What I was watching was this woman's breath condensing in the air (like all our breaths were). Then I realised she was wearing a face mask. Her breath wasn't steaming out of the sides of her mask, nor up her nostrils, nor out of the bottom of her face area. It was billowing straight out through the mask - great big puffs of it. Even I couldn't believe what I was seeing for a moment. If I was 99% sure that face masks were ineffective at stopping Covid, from that moment on, I am 100% sure.
I wish I had something on me to record what I saw - I would have sent it to every media channel and government possible. It would probably have been ignored, though, as it just doesn't fit in with the politics of being seen to be 'doing something'.