Http2 has efficiency gains at the transport later but not typically at the application tier. Having a single http request lets you things like handling authentication, fetching common state (user object), etc a single time for a batch request. Http2 doesn’t help you here.
For one, having it be transactional.
>With HTTP2 you can send a ton of requests in parallel.
That's orthogonal. And they still have a cost (in time and size of transfer).