Arcade and store are two different beasts.
And games with more than 30 Mo can be uploaded to the store, the actual problem with most uploads is the speed of connexion which makes it so that it resets during the transfer. (In those case, upload by URL through a service like dropbox does tend to help since dropbox has a better transfer rate)
As notified in the release topic for the beta arcade :
All third party plugins supported!All game sizes supported, no max widths!Games up to 50mb uncompressed supportedAttach capx files up to 50mb in size to games
So I guess the issue is somewhere else.
At worst, send your exported zip to the support and it will be investigated.
But 30 Mo is no issue.