The other possibility is that you kept things that fit the old you rather than the current you, and the cleanout just made them more visible. If a garment felt off before the cull it will feel worse now that it isn't hiding in a crowd.
Pilling is friction, not washing, and it shows up exactly where two surfaces rub — underarms, sides, seatbelt line, bag strap. Your routine is fine. What's actually driving it is fibre length: cheaper merino is spun from short staple, and short fibre ends work loose and tangle. A sweater at three times the price with the same fibre content can pill dramatically less because the yarn is combed longer staple.
Practical fixes:
- de-pill with a battery fabric shaver, not a comb or tape, and do it on a flat hard surface
- do it after the first two wears, not after it looks bad; the loose fibre gets pulled out and the fabric stabilises
- alternate sweaters instead of wearing one three days running
It slows a lot. The first crop of pills is the short ends near the surface; once those are gone the remaining fibre is anchored in the twist. Shave conservatively — light passes, don't press — and it'll stop being a weekly job after a couple of rounds.
Agree with the practical take, but the tailor still has to move the buttons up and the old buttonholes will show as faint marks on some fabrics. On a tweed you'll never see it, on a smooth worsted you might.
Pinch test: standing, grab the fabric at the side of your hip. If you can't pinch about an inch, there isn't enough room there full stop.