They just launched HBO Now, so your complaint is moot.
I know, but as I'm in the UK, my complaint remains perfectly valid.
Here your legal options are basically limited to either getting Sky or relying on one of the very limited number of on-line options. All of these require dedicated equipment and/or work out absurdly expensive if GoT is the only exclusive show on the service that you're interested in watching. As I understand it, you're also still likely to get interrupted by ad breaks and logos/banners spammed all over the screen -- an insultingly inferior experience to just playing a disc and enjoying the show, and you're paying a premium for the "privilege".
Personally, all I'd need to avoid the disappointment is a simple and reasonably priced pay-per-view option to watch in sync with everyone else. With no real effort at all they could at least release the box set of discs as soon as the season has finished like every other show ever. In practice that would probably still avoid the worst of the spoilers, because usually people are pretty good about not assuming everyone saw this show live. The biggest spoilers I had for season 4, which I just finished watching, were all the trailers and promos for season 5, which obviously only start happening nearly a year after season 4 finished its first run.