You can resize the window and font to your hearts desire on x86 windows. I don't see the big difference running windows on a 8 inch tablet or a six inch phone less than six I see your point , but that's where a phone mode would come into play . No not every legacy program would work great but it's much better than what we have now
OK, so we got a phone mode. We're back to square one, its not any better off than W10M. Legacy programs aren't going to work, and if they do, they'll be nigh unusable (combined with the portrait orientation too) and the phone might inherit the negatives of desktop Windows too.
But say it does work well and we can't tell it apart from W10M in use. It does virtually nothing for the app gap. It might help band-aid it, but things that people do on phones may not be on x86 Windows and vice versa.
Turn-by-turn navigation? Not really.
Social apps like Snapchat, Yik Yak, Facebook Messenger, etc? They won't work any better. (in fact, many would just continue ignoring the platform as it was before - Snapchat doesn't even make a tablet version for iOS.)
But sure, I think if they can cram a full PC or even a full Windows RT experience into Continuum, it'll be a big plus in my eyes.
But I fear not for most people. I fear Microsoft is out of silver bullets.