Most of my bikes, except for 2 have downtube friction shifters, the other two are briftors, I have no problems with downtube shifters, I've been using them for 60 years! Once you get use to them, which doesn't take long, they work beautifully. I used to race in the mountains with downtube friction shifters, as did everyone else back then.

Downtube shifters are a lot like a manual transmission in a car, today people don't like those either, yet we all knew how back in the day to use those, it was no big deal.