I consider tabs for indentation a failed concept.

The idea is good, but it evidently failed. Most guidelines and newer Tools recommend or require or use spaces for indent. They have their reasons too.

The prevalence of spaces makes it hard to make a contrary argument for tabs. By now, I don't think it's worth even if it had reasonable advantages.

Editors/IDEs that parse syntax can adjust space indent too. A mixture for indent and alignment is not obvious for everyone (I always display whitespace in my editors and am deliberate and consistent, but many people and editor defaults won't be). Some defaults of four or eight space-width tab display is atrociously wasteful and inaccessible.

Spaces are a good enough baseline. It works well enough. And most importantly it works consistently. That's why it won in prevalence and use.