Well I am very biased, because my everyday clothes are mostly 18th century menswear inspired, but for a list as short as 5 it's good to narrow it down!
1. 18th century shirts. Big puffy soft linen shirts. Best shirts. Comfiest shirts. Though tragically, since they get softer with more washing, they're at their absolute most comfortable right before they wear out.
(This one's from the post where I copied the tiddy-out violinist painting.)
Besides being the nicest softest comfiest, they're also the most economical, being made entirely from rectangles. And they're versatile, they look good with lots of different garments! Someday I will do a very detailed youtube tutorial for my machine sewn shirt method. I've done so many now that I think I've finally got it down.
2. Adjustable waistbands. Why did this ever stop being a thing? 18th century breeches have lacing at the back, then in the 19th century trousers have a buckle tab.
Now they do not, even though we're all still humans with bodies that change. (These are my orange silk breeches)
Do you know how many hours of my life I've spent taking in or letting out the waist seams of modern trousers? I don't know either, but I've been an alterations tailor since 2019, so it's got to be a fair amount.
All that waist altering wouldn't be necessary if they still made them adjustable! Waistlines fluctuate, so too should waistbands!!
3. Shoulder capes attached to coats. This was a thing in the late 18th century, and in the 19th, and I think into the early 20th too. It adds extra protection from the rain and snow, and it looks cool.
You can make them long or short, and stack them up like pancakes or just have one. I've got 2 small ones on my corduroy coat, and one on my dark blue wool. Both cut from almost the same 1790's-ish pattern.
I also want to give a shoutout to fitted sleeves! I love me some two piece sleeves with a distinct elbow! And the coat pockets were bigger back then.
If it's cold in your apartment you need slippers for the feets and a cap for the head. Speaking of which.
5. Medieval hoods. This one is wayyy outside my usual era, but the wintery below-freezing weather has just started here and the knit hat I've been wearing isn't quite long enough to cover my ears. I want to make a simple hat with ear flaps, but I also wouldn't be opposed to trying to work something vaguely similar to this into my wardrobe. It looks so warm!
That's some of the main things I think we should bring back! There are lots of other things too, like men's nightgowns, and waistcoats with little scenes embroidered on them, but for this list I tried to be mostly practical.