This way of thinking would only hurt AirVPN.
The reason 'all other providers' are crap isn't because they can't better, it's their business decision. iirc AirVPN said their 'allocation' is 2 mbits per customer, now I can't say how that is applied but you can see very clearly thanks to transparency how many people are connected and how much bandwidth each server is currently using up. Scaling up is no problem, but it must be a business decision. If needed I'm sure they could fire up 10s of new servers within days etc. But an 'explosion' ain't gonna happen because they don't waste money on advertising, instead if you want to help - just help.
Why are other VPN so bad? Because of overselling. There's a difference whether your servers run at 30% capacity or 80% (aka overloaded), it's money for the business and quality of service to the customer. If servers run at more than 70-80% then your latency will suffer, packet drops etc.
The reason why AirVPN is solid is because they chose to. The reason why some other providers are shit is because they chose to (or are incompetent in addition to this). @NoiselessOwl says to rely on 'word-of-mouth' but then doesn't personally advertise AirVPN at all (I understand user's own word-of-mouth)? That goes against that idea. Users advertising themselves is the breeze of air that keeps AirVPN alive. Otherwise old customers would slowly drop out and no newcomers join.
You can't singlehandedly make AirVPN become like a mainstream provider. I believe them to increase capacity when needed. Hell I doubt even a big youtuber or anything of sorts would make a dent if they were to advertise once (for free or not).
I disagree strongly with the previous poster and want to say: Advertise AirVPN as best as you can (casually, it aint a chore nor a job)! If you want to see greatness, you need to help spread greatness. Don't leave less knowledgable users stuck to the shitty mainstream VPN services.
PS: Does any other VPN out there pay as much close attention to the legal framework of server countries as AirVPN does? It's one of the main goals of a VPN provider! To ensure the security of your data!