True, it is a bit formal, but correct.

As a native-French, I would instead probably say

Comment se fait-il que personne ne soit jamais à l’heure aux réunions ?

You could simply say (a bit familiar, not written French)

Comment ça se fait que personne ne soit jamais à l’heure ? (aux réunions)
or
Comment est-ce possible que jamais personne n’est à l’heure aux réunions ?

The first one that comes to my mind (apart from “pourquoi“) is:

Comment ça se fait que […] ?

It’s the non-inverted version of “comment se fait-il” and that makes it way more informal. I don’t think the subjonctive is a problem here.

You can use a lot of variations that can slightly change the meaning, such as:

• Comment expliquer que […]
• Qu’est-ce que qui fait que […] (this one, you use the present tense after, but it sounds a bit heavy in my point of view)
• Pourquoi […] (which is just “why” so it doesn’t convey the meaning of trying to explain the “how” precisely).
• Comment est-ce possible que […] / Comment c’est possible que […] (more informal)

and so on.