I did hold that belief for some time, but I solved it with the most reliable notification-method I came across thus far, and that's plain simple email from my own domain.
I understand this is not possible for specific apps that need smartphone notifications to function properly, but when you think about it: a lot of (web)apps don't need that.
In general, one might need less notifications than one thinks.
>>rambam+(OP)
As a vendor, notifications sell more. As someone who sells things, you need to outsell your competition. Therefore, as a vendor, you need more notifications than you think.