I've been stuck in my share of traffic with a manual, and don't see the problem...
Part of the difference in how we see that may be that my knees are a couple decades older than yours.
I rarely drive a manual truck in traffic. Most likely if I'm stuck in traffic I'm in my manual transmission Corvette. Having to full-stroke that pedal a lot quickly leads to knee pain which extended long enough leads to difficulty controlling the clutch as finely as I'd like.
Its not big deal in my usual commute but if I have to enter or exit the big city during peak traffic I'd regret taking that car because of the manual transmission and the clutch. And yeah I've been thinking of replacing it with an automatic.
That Corvette experience does impact my thinking when considering what I'd prefer in a truck I'm building or buying.