Having been flying for some years before the Collins FD 108 was introduced on B707s, using such things as Decca and Omega for navigation and a rudimentary PDCS to assist the Flight Engineer in manually setting engine power, I can assure you that piloting skills were very different then, compared to today. Different.
All we ever did then was 'basic' flying. NAV switch, what is that?
Now we have Auto-pilots engaged at Take off, Lnav and Vnav engaged almost as we lift off and spend our time 'monitoring' the automatics.
If you lose all your automatic systems then a pilot without 'basic' flying skills will have a very hard time keeping the show on an even keel until he can land and get it all fixed.
Observing and monitoring the closed loop system from outside is very different from being in the loop itself, much less constituting the entire loop if all is lost.
However, my advice would be to look at the statistics from Mess'rs Boeing and Airbus regarding FD failures in the last 20 years (almost zero) and compare that with the number of incorrectly calculated performance data, engine failures/flame-outs, incorrect configurations, loss of spatial awareness, lack of ability in adverse weather and all the other elements that cause the majority of accidents and practice accordingly.
Flying a departure or an arrival without a FD hardly constitutes an increase in one's 'basic' flying skills. It merely removes those features built into the very system that has been installed to increase flight safety.
If your reasoning is that you ought to 'practice' raw data flying in case the automatics fail, then what is the point of doing such practice when the weather is severe CAVOK? Surely, you are reasoning that you need these skills in the event it all goes tits-up when the weather is awful? If the weather is fine then simply look out of the window and keep some power on until the wheels touch the ground.
Much better to hone your flight planning, briefing, performance calculations, normal and non normal procedures and getting the flare right than wasting your time flying around with the FD switched off!
Priorities.........