Purely decorative clothing (things like little skirts or lederhosen) for animals is, in my opinion, indeed nonsense.
But with
functional clothing, I see it very differently. For very young, old, or sick dogs, and those with little fur or no undercoat, clothing can definitely make sense and may help prevent illnesses (e.g. colds, bladder infections).
My dogs (Boxer-Lab mixes without undercoats) got cold or still get cold in freezing temperatures and then wear a
winter coat, e.g.
Pelerin with the belly protection from the
Add-on Set
A
raincoat can also definitely make sense, depending on the dog.

A
shirt or bodysuit as wound protection or to prevent licking (after an injury or surgery) is more comfortable for many dogs to wear than a huge cone around their neck.
A
bathrobe after a downpour or swimming makes drying off easier and can help protect against getting chilled, e.g. the sewing pattern
Tirim.
A
heat or incontinence panty (such as the sewing pattern
Colleen) of course mainly protects the furnishings, but for many dogs it is also more comfortable than, for example, lying in their waste at night.
Paw shoes can protect against burns from hot asphalt or injuries, for example on longer hikes.
And
bandanas, etc. are often used for identification (e.g. therapy dogs, assistance dogs, “yellow dogs,” search dogs), or can be used in training to help the dog switch from leisure mode to work mode. Sewing pattern
Dandy.
My personal conclusion is: clothing YES, when it makes sense and doesn’t unnecessarily restrict the dog 🐾