There is absolutely nothing inherent about a Hill bow that will prevent anyone from shooting at their personal best, and there is no reason to believe that a r/d longbow with a sculpted grip with all sorts of placement details and palm swell will increase accuracy.
Archers are no different than the general public. We want something more, something just out of reach, and something more is delivered to us with commercial ads and endorsements and the imaginings of others. In traditional archery that may include more space age materials and radical limb profiles and arrow speed claims. A lot of us want more advantage in our equipment, when what we could benefit most from is becoming more skillful as archers.
One of the most interesting aspects of compound shooters is how much time they spend fiddling with their bows. Bolting on this thing, taking off that thing, adjusting this and that, buying a new thing, and on and on. They are under the belief that the "bow" is THE thing, and if the bow is "out of adjustment" or has other breakdowns their poor accuracy can be easily explained away. I see some of this mind set creeping into traditional circles. If we are not shooting well it is very rarely about the bow, or the next bow, it is almost always about us as archers.
A Howard Hill bow is as fine a traditional bow as can be had. It has evolved and been refined over many years, and thousands of archers shoot them with great accuracy. If you believe that you cannot shoot A Hill bow well, or any trad bow for that matter, you will not be able to shoot them well. If you believe that a straight grip will put you at a disadvantage, it will. If you believe that a highly sculpted grip on a r/d longbow will make you a better archer, it will. It is 90% about our expectations and 10% about the bow.
And for all of you guys and gals out there who may have one of the "simpler" bows, be it a Hill or a fine selfbow or whatever you may shoot, take heart; if you love your bow and you practice consistently you will have in your hand the best bow on the planet, for you, and what other bow could you possibly want?