I've answered this question many times, there aren't many RB's out there who I'm in love with right now, but I'd still rather have one that's younger, has some scope, and can retain some inherent value, who we won't be struggling to get off the payroll in two years time, than an older one I don't love much either.
If we are selling Aurier for 20m Eur, then why not spend 15m Eur and get Hakimi - another who's played as a RWB but has also played as a RB.
Back up option, Atal is a player, like Doherty, who's been used predominantly as a RWB, but is much quicker than Doherty. Would almost certainly cost less/same and is about 4 years younger.
I really don't see Doherty as much of an upgrade on Aurier generally. And I say that as someone who doesn't like Aurier loads.