There appears to be some revisionist history at work here.
Before the influx of low-cost apochromats, long-focus achromats were generally considered to be among the sharpest optical systems available. Forty or fifty years ago when I started observing, a 4 inch achromatic refractor was around $1,000 and many observers, myself included, were happy to pay this price at a time when 6 inch reflectors could be had for less than half this amount.
I am not contending in this post that achromats, even of long focus, are superior or even necessarily equal to today's better quality apos. I am responding to the OPs question as to whether achros are sharp planetary scopes. To this end it is clear that many authors and observers in the past thought they were. Not just myself and a some other posters on this thread.
So-o-o-o, of course long- focus achromats are sharp planetary scopes. Just because some modern day apos may arguably be even sharper doesn't mean this is no longer the case.
I am not seeing any revisionist history, I am seeing the progress over the last 50 years being documented here.
Planetary observation has progressed dramatically over the last 50 years. Large Newtonians with thin quartz mirrors and near perfect optics with careful attention to thermal equilibrium were no where on the horizon. SCTs and high end Maks were in their infancy. The apo refractor was very uncommon and were not part of the consciousness of the amateur community. Today's planetary scope is far more capable than those of 50 years ago.
And when it comes to slow achromats that people paid $1000 for, some were sharp, some weren't so sharp. That's the perspective of history.
So, I think one can say that an achromat with a chromatic ratio near 5 can be provide reasonably contrasty, reasonable crisp views but as you say, in todays world, they won't be the sharpest nor will they be the most contrasty.