Well, they're not useless from a systems perspective, in that sometimes they can help identify/differentiate between people with very common names.This is totally correct. Middle names are useless in Canada.
But I look at it differently: the point of middle names is entirely social - to mean whatever the family and their social circle wants it to mean. It's just a second given name. Whether that's a patronymic (like in many languages incl Slavic) or mother's family name (eg Spanish tradition, still used in some countries with historic/cultural link to Spain) or just a grandparent or treasured relative, that's fine.
Obviously some want it to be a 'second family name', which is also cool - but it won't have that significance here unless somehow included in the last name field (which might require a legal change fo name).
But again: most Canadians won't get fussed about it. Use what you want in the contexts you want it used and most people will respect it.