I'm quite surprised this question has no good answers yet, so I'll do my best to create one.
(don't read this if you only care about the solution)
With some changes to YouTube, Google got a bad reputation for changing things against the users in order to make more money directly or indirectly. This also includes the "What to watch" feature, which promotes content that Google thinks you want to see. It has been said that this was done to help new users find content on YouTube, mot likely showing you content from promoted channels, or as some call it, "YouTube Partners".
The main problem is, they overthought it, or, depending of the way you perceive it, underthinked it. Most of those who complain about the newer layouts are old users of the site, and throughout the months/years we've been there we built up this list of people whose content we actually care about. They don't care for the fact that the list of things you like is right there, that list of people you want to watch regularly, all in one place. Too bad money is more important than their very own users' feedback.
Since there's no sight of an option to allows setting your default homepage to the "My subscriptions > Uploads only" page, your best bet is to bookmark that page instead of https://youtube.com/. Currently, it's URL is https://www.youtube.com/feed/subscriptions. This seems to be the only solution (without using addons) currently, as Google does not care about giving us an option to change it.
Solutions involving extensions/addons
http://youtube.com/feed/subscriptions, and also change any and all links on the webpage which point there. You will need to install one of the following extensions for this, depending on your browser:
Sadly, there's no plugin support at all in IE (at least up until version 11), but to be honest, if you regularly use Internet Explorer, then you should get used to the fact that it just makes your browsing experience worse, and I suggest you get an actual browser instead of a thing that's capable of displaying web pages to some degree.
Here's a link to the userscript. With Chrome or Firefox and the appropriate addons installed, you should be able to install the script just by pressing the "Raw" button in the source code header. The same should happen in Opera or Safari too, but I could not test it.