A tailored suit, but indeed, every tailored piece of clothing will always have the best fit and comfort. That's trivial. Even your sweat suit would benefit from being a tailored sweat suit.
I have non standard measurements and buying trousers has always been a chore (a cm lower shoulder, a 1/2 cm shorter leg, cyclist quads, life influences body). I've now started to use AI to pre-select brands and fits that might suit my sizing. Which is actually just moving somewhat towards at least 'fitted' clothing. The future of adult and sustainable fashion 'should' be made to measure.
Also you do make it seem like you start from clown suits, the suits I've tailored start already pretty good and go to great. They don't start with all that extra fabric you describe in a way that would make them uncomfortable.
I guess we need the distinction of made vs. made to fit (a suit that is tailored post-production) and made to measure (a tailor-made suite; each piece of cloth size for a unique product). Best fitting is made to measure and that is what I am referring to.
It isn’t trivial; any time a piece of clothing pinches or pulls that is what makes it uncomfortable, and loose clothing doesn’t do that by definition. That means any kind of shaped or fitted clothing including tailoring can only be less-comfortable than loose clothing and approach being equally-comfortable as an upper limit, getting closer with a more skilled tailor.
That means tailoring is mainly for looks - I.e. the only reason tailored clothes exist at all is because wearing a looks bad; start with a super comfortable ‘bag’ and cinch it as close to your body shape as possible so it doesn’t look like a bag, and looks better, get as close as possible without losing that comfort.
Maybe it’s cold and the extra airiness is working against you.
Maybe the clothes rustle and rub more when you move.
How do (non-elastic) pants stay up, without some minimal measurement for the waist?
I own some more baggy T-shirts and layering with a sweater feels more uncomfortable because the clothes will fold in places you don’t want them to with a sweater on, which is not a problem for more trim fit clothes.
The future is already here. You can order custom sizes from many designers quite easily on the web, it's just not cheap. Few people are willing spend a few hundred or thousand on every outfit when the same thing can be had for $20 mass-produced.
But when my wife made a shirt after my actual measurements as an experiment, it did not squeeze my neck and was very comfortable. I loved that shirt and used it for many years until it fell apart (unfortunately it wasn't made of the finest materials, and I don't have the wife any longer either).
So I'd think adjustments can absolutely help comfort.