When someone is powerfull enough to be defacto ruler it counts in my view. However. Look at Constitutional Monarchy. Many Prime Ministers in the UK were powerful at points so at least should give an effect, (not a regency). I mearly argued that the abilities of non monarch rulers should be related to the country and that the heirs should be influenced by event triggers to improve or worsen their abilities. The same with monarchs. There should be a two thirds to one third balance for good 2/3 and bad 1/3 as to be fair to the player because bad is fairly likley to happen and the usuall bad heir could result in a crap monarch.
Someone like Richelieu is hard to model in game, but I think the current system is fine as is. You can get really good advisors in different areas that can have a huge effect on your country that can represent the effect of great mean like Richelieu. This is especially the case with HTTT, where you can hand pick who you want and your cultural/naval/army tradition determines how good they are. And despite perhaps at time wielding enough influence to be considered a regent of sorts, they were still subject to the whims of the king, and thus were never really anything more than glorified advisors. An example of what I am talking about would be Cardinal Wolsey. He held considerable sway over Henry VIII and had enormous power early in his reign. But when Wolsey couldn't give Henry what he wanted, a marriage annulment, he eventually lost favor and was sacked.
Besides, is isn't as though when you have 3/3/3 king that you yourself go stupid. Aside from not being able to execute certain decisions, you can do everything else you want to, and your nation can still be powerful. If anything, you don't get enough penalties for having a horrible ruler. There are countless examples throughout history of rulers that practically threw away their kingdoms, like Czar Nicholas II.
