There's an extension I used to use called 'StayFocusd'. It's intended for blocking distracting websites, you choose your only rules, and it's really strict about enforcing them - you can only change blocking rules on days that aren't today, for example, to stop you from temporarily unblocking a website. You can either block them completely, or give them a daily limit.

You could install that and put Reddit on it. If you really need Reddit for something (say, getting a relevant search result in a sea of SEO), you'll still be able to bypass the extension to view it. But it will make you type a paragraph accurately to make sure it's a conscious decision. You can't simply disable the extension.