I think trust people to know and do what they want: left click or middle click. The problem with making the new-tab choice for them is they can't click in such a way as to keep the same tab. I have literally written browser extensions to fix auto-new-tab links, it's that frustrating.
I'm the opposite. I actually wrote a small browser extension to make HN links open in a new tab because it annoys me so much.
I can't disagree with what others have said about making it user-choice though. Maybe some kind of toggle switch that lets users set the behavior one way or the other would work?
A link should always open in the same tab by default, unless there’s a compelling reason otherwise: for users who prefer to open in a new tab (like myself) they can use the appropriate shortcuts, menu options or click combinations. If you configure links to open in a new tab, it’s impossible for a user to open it in the same tab.
Following this tangent, I think Twitter has some of the worst dark pattern UX about this. Sure, middle click opens a new tab but it also hijacks focus instead of loading in the background. It's really frustrating when I see X interesting things and want to open them all at once and then go through the tabs.