You seem to think that a players has the character he deserves. What if you start as a 40ish count which already has an adult heir whose stats kinda suck, for example? What are you going to say, you'd deserve to be crushed because you'd choose a loser of a count? Oh, wait, just assassinate him, that makes so much sense!
What you call "good ruler" is to be, in my opinion, a gamey ruler. Thou shall nevah have any vassal below 90 relation, bribe them all with gold, squeeze them of any levy they can produce, or you're a bad ruler and deserve to lose! What actual king had no enemy in his court, no internal threat? What actual ruler went elective because it will mean more troops and super breeds of heir? What actual ruler revoked city titiles to gather monster taxes to hire ten times as much of mercenary than he has levies?
You are acting like an idiot now, if you play as a count and have an adventurer declare war on you and you can not win, then you lose the game. What you want to remove a mechanic because it made you cry? What other games do you play? Do you also complain about the mechanics in those games that make you lose and demand they get nerfed or removed so you don't have to actually play the game to win. You choose to play as a count because you want the challenge and when you get a challenge you what complain?
My rulers rarely have good relations with vassals, I typically run my vassals borderline rebellious, because with the current system it allows you to do it. I just took over a kingdom and inheritted another, sacrificed my brother, destroyed the two kingdom titles and probability of rebellion is "high" but I use my councillors to improve relations and stop faction joining. So they just never revolt, if there is a risk you can also use the free opinion modifiers called gifting cash and honourary titles, or if you are so inclined just use the free opinion exploit. If I have all vassals with 90 opinion of me then I'd be very surprised, I used to play the whole elective vassal love game, but that is actually not as effective as my current approach with Primogeniture and traits like cruel, wroth, greedy and the like. Vassals have become a side note in most of my games, and I only look at them every couple of years to move my councillors around and make sure everything is within expected parameters.
I never imprison and banish temples and cities for cash, you do not need it. If you have cash issues, then you need to learn how to tax your vassals. You set it to large or harsh, I typically just run on large but with my last game creating Isreal, I set it to Harsh straight away with an incoming holy war and never reduced it back. From there I was able to run 2 of the horse archer mercs for decades holy warring and expanding with little contest. Then add in the retinues later in the expansion and vassals very rarely for multiple war fronts, Isreal created before(pretty sure it was before) 1066. I had 1 adventurer claim against my realm, who was some catholic living Greece, who showed up with 30k troops. What a joke I just took my horse archers over and dealt with it (12k troops vs 24k after letting them seige a few holdings - no contest). The only other invasion was the Seljuk invasion which hotdropped from space 60k troops right next to my capital, I lost that war (first time I lost a war to them ever), but I didn't come here and complain. I have however noted it in several threads as something that could be improved(no warning), but you deal with it and move on.
Just because you or someone else likes to run elective rulers and grease the pockets of their vassals, does not mean others play that same way. I rule them with an iron fist and squeeze every cent I can, if they get upity, they go to meet kali(in my current game at least) and replaced. If I need troops, I hire mercs that is what they are for. So I guess I roleplay more than those other people you are talking about, not exclusively obviously. Currently thinking about switching to buddist to change my heir to my 3rd born who got strong, who is likely to be betrothed to his cousin who is also strong, because why the fuck not? My current heir is married to a tri kingdom princess so it is not very likely.
No claimant wars on me, or even adventurers, nothing planned and 100 years into the game, so either I am doing something right or those that get constant adventurers are doing it wrong. Don't want claimant host? Land your children and silbings, and tax them. You want troops? Hire Mercs. More than one way to play this game, whether you are being a kind and generous liege or cruel and wrothful. Both approaches I will point out however are roleplaying. You might call them "gamey" rulers (also gamey does not mean what you think it does) but in reality they are roleplayed by people wanting to be kind and generous to their vassals, sure they go the extra mile with elective and playing genetics but it is not needed and typically causes more problems in the long run.
By good management I mean, de jure drift everything you can into your primary title. Make sure your vassals are your culture/religion, do not exceed your grasp until these few things are done. When they are you are able to expand further and increase your de jure realm as you go. In my Jewish game I never created other kingdoms or even empires, once the duchies started drifting into the realm my power grew even faster allowing me to rush to Jerusalem and take it all inside 2 decades, even against the shia caliph who controlled all of Africa and the Abbassid/Seljuk alliance. If your realm is spread thin over several kingdoms and you have precious few de jure vassals, you are going to have a bad time. Realm management is important and part of the game, ignoring it leads to people not realising why they get hit by so many troops at once that they can not defend against.