This is a naive assessment. Imgur is running a business and with that comes all the surrounding cruft Harry is complaining about. I hate including marketing and tag management tools in my project at work but that is what the business wants.
My beef is with a ‘mobile-optimised’ image hosting platform taking over 40s to display an image on mobile.
That wasn't an engineering decision - it was a business decision made to force people to switch to the app. Ever try browsing imgur on mobile web? You can't - it keeps popping up the 'download the app' button. Infinite scrolling breaks because of that popup (by design). If you don't want to support a business that tries to force people to use their app by making the mobile web version horrible you don't have to.
There's no hypocrisy in using something while complaining that it's absolutely terrible. (Particularly if there isn't a real alternative; "don't ever open any link to any image hosted on imgur even though you'd prefer the person had hosted it somewhere else" is not reasonable.)