Once Android has the same desktop dockability, the only advantage of Continuum will be the ability to run legacy Windows apps. Not a small advantage, that - but the keyword is legacy. The market for people that want a pricey phone with crappy phone apps so they can dock it to use legacy X86 Windows apps is pretty small.
But that's the thing, Microsoft's solution doesn't even do that; because their Windows Phone (now Windows 10 Mobile) devices run on ARM, they can't run legacy x86 Windows apps, and people can't even recompile those for ARM even if they wanted to and in the cases where there'd be no issues because Microsoft won't let you distribute and install non-'Metro' (or whatever exactly they're calling it now; UWP, I think?) code on ARM-based versions of Windows. The only stuff you can run using Continuum is Windows Store non-legacy apps, which are actually a far smaller set of applications than those available on the Google Play Store or iOS App Store. Hell, my old Nokia N9, the product left in a ditch as Nokia jumped foolishly on the Windows Phone bandwagon, has a more vibrant developer community with a better selection of applications than Windows Phone managed for quite a while, so leaning on the new-apps side of the strategy wasn't ever going to be a winning play for Microsoft.
Microsoft's mobile offerings floundered for many reasons, and no small part of it was how they completely failed to take advantage of their entrenched positioning in the desktop market.