I'm not sure that I get your point. My comment was about hereditary monarchs and made no mention of what else may work in monarchy's stead. There are many flavors of parliamentary systems some better than others. I for one believe that our 'easy democracy' policies that continually creep towards a 'majority rule' system are deeply flawed. Democracy should be a check on authority, not the primary system of governance; and it should be reserved for those willing to put out a modest effort to participate. Otherwise you will end up with governments such as the Mexican where you in essence buy your votes with favors of public money or systems where the populous vote in the savior du jour... or their surrogates.
However there are implicit ideas in your comments that I find flawed. Some are related to an efficient king and the other about a necessarily powerful legislative organization.
Ultimately I believe that a government should only exist and have the power to prevent the violation of the innate rights of its citizens. This doesn't mean that government (or its people) can simply recast privileges as rights either as we are wont to do nowadays. The first right being that of self-owership; other rights that derive from that one axiomatic right. And don't forget that for you to have a 'right' there cannot be an obligation on any other person for you to exercise it, other than the obligation to not forcibly interfere with your exercise of your rights. A government limited to that single purpose would be as efficient as it needed to be... and moral to boot.
Second related to an efficient king. I would argue that there can be no such thing and that what you describe in little more than a tyrant. You say that there is, "no bitching". Why? Because there is no freedom to complain under such a system? I have found that in any group of over 100 people there are few that completely agree, so the only way that your point comes to fruition is if the king forcibly intervenes in his citizens' right to speak their minds. And even that can be messy: witness Tunisia, Egypt, Libya, Syria, etc. You say a fair policy will be obeyed, but fair to whom? I guess if you're suppressing speech that's much less of a worry, especially if you are suppressing only a minority which is producing the prosperity of which you speak. In truth though the only policy such a good king could maintain while increasing the genuine prosperity of his people is to rule very little: protect their rights and nothing more But then you run into that problem of the hereditary roll of the dice. A bad king may be the good king's son/daughter. Just how efficient are decades of good leadership followed by decades of bad? A limited democratic republic, wherein the politicians had the single job of upholding the enshrined rights of the people, seems to me to be far more efficient and durable. We may have been slowly losing sight of that in the US (for many decades now)... but that basic vision has sustained for over a century and the strength built during those decades has carried us for over a century more.