Numbers. Numbers are how we determine what is 'most' of the fan base. There is no other way to determine that.
What is the percentage of D&D products sold via online purchasing compared to shops? It could be interesting to know: - particularly if there are differences along national lines.
Do the figures distinguish between 5e products sold in places like bookshops, and those in games stores?
I have a play area in my house. I have have friends and they have friends. We have a great time playing together. This is how the game is growing.
And its really cool that you and your friends are affluent enough to have houses with rooms big enough to hold your games in.
I'm fortunate to be a member of a university club that can provide a venue for some SATT games. - Although it can get annoying when everyone at the table next to you starts shouting.

I'm also fortunate to have a couple of games stores nearby where D&D is played: they regularly organise starter one-shots and help groups get together. Sometimes these beginners and groups end up playing in the store, sometimes the group moves to play elsewhere once established. This is
also how the game is growing.
I have no desire to play with strangers at gaming stores.
That's OK. It sounds like you're lucky enough not not have to.
I'm pretty sure that no one here is suggesting that you be forced to.
Donating to stores will absolutely hurt. Maybe you aren't aware that there are people who play this game who don't have a lot of money. I would venture to say it is a lot of people as new players are likely to be young and the millennial generation is poor and in debt.
A donation to a store means buying fewer books from WotC and having fewer supplies for playing the actual game. That is hurting the game.
Sure, if you're rich, donate where you like.
Your point about the finances of most of the newcomers to the hobby is well-made. Buying a house or even flat with a decent-sized room can be expensive. Many find it easier to pay a couple of pounds for a game in a store every week or similar. When the choice is donating to a store or
not playing the game, then buying products or hiring tables at a store becomes
better for the hobby than just getting your D&D kicks through Twitch or Youtube.
Sure, if you're not a newcomer and already have a gaming space and an established group, feel free to save a few quid.