Gmail may not have the security features that Protonmail has but Gmail does provide a more fuller suite of services that can be used across multiple platforms. For example Gmail has mobile apps, calendaring, etc while Protonmail has yet to mature to that level functionality.
Another limitation is that at the moment you need to wait for at least 3-4 weeks (if not longer) to get a Protonmail account.
You mis the whole point here. Protonmail isn't meant to be used as mainstream email application. If that was the case, it would offer a much better free service experience to compete with the rest.
Other than that, what do you mean with that you have to wait 3 to 4 weeks to get an account? You can sign up and start sending and receiving emails with protonmail within 3 minutes.
You need to see the bigger picture here. Protonmail is funded by a "donation" and "subscription" service and would always lack the funding to build capacity like Google. When they run out of resources, they rely on "donations" to increase their capacity to allow for more people to join their service.
They offer much more than Gmail or Yahoo Mail, because you have full encrypted and private email services with them. You have absolutely no privacy with other FREE email services, because they use your information for marketing and to supply information to their government. < As Edward Snowden has proven >
I think the Swiss has been turned by the USA, so services like this will come under constant attacks, like they have been with continuous DosS attacks recently. ^grrrrrrrr^