Mostly my handsewing is for historical clothing*, but yes, you can sew everything by hand. I'm rather bad at using a sewing machine, really, so if I want it to come out nice I do it by hand. For instance, the silk chiffon sleeves and the concave/convex curve at the bust (bane of every non-professional machine sewer) on my wedding dress were done by hand.
* tailor-made historical clothing is my intended side hustle...after I get my husband's historical wardrobe sorted out
For reference, I sewed a simple skirt pleated into a waistband one weekend while at a family reunion. For a gown with several layers of interlining padstitched together (to provide structure), I took a month (while working a full time job). For a historically-inaccurate gown (interlining with hemp cord for structure) done on sewing machine, cutting and assembly would be a full Saturday (and then a few hours to hand-stitch all the eyelets).
Now, you want to talk really "make by hand"... my mom's Christmas present next year will be sewn from fabric I will weave specifically for it. I don't intend to spin the yarn for that project (though I have spun for weaving before, but only for weft not warp), as I've never spun tweed. That does get me thinking a bit, though...