i.reddit.com is way more basic than old.reddit.com. It's intended for ancient cell phones or the slowest of slow connections. It's actually pretty impressive that it works at all these days.
Fundamentally all reddit is is some comments and upvotes in a database combined with a ranking algorithm of some kind. Other than scale, the actual core functionality is exceedingly basic, so I hope they maintain these old versions (mainly old.reddit) for a long, long time.
i.reddit.com has infinite scrolling, so it's worse.
You can also append .compact to any url for a simple mobile- friendly version of reddit. I refuse to use the app and this works great for me.
Seconding the Compact version - at one point the site upgrade / redesign reached the point where it was unusable in my browser. Compact saved the day, and makes the experience much smoother to a fellow app-refuser.