Present good script… no client buys it. Present trash script… instantly bought. Why does this always happen? What makes trash buyable?

It’s safe

I get what you’re saying, and to a degree I agree and sympathize. But why do some agencies produce great work (or more of it) and others can’t seem to be able to?
It either boils to one or more of 3 things: The client, the creative talent, or the ability to sell the work.
I’m a freelancer and have worked with all types of agencies. From small regional shops you’ve never heard of to creative powerhouses that everyone admires and every type of agency in between.
You’d be surprised, but talent is rarely the issue. At least at the low to mid levels. It’s the leadership talent that makes a bigger difference. Starting from the fact that at the “not so creative” agencies, I routinely see good ideas killed internally by CDs or above because these people have no discernment of what makes an idea good or not. So even if creatives came up with good shit, it almost never makes it to the client. A lot of it is dismissed right away also with “the client is never going to go for that” even if it’s totally on brief, budget, etc.
The agencies that manage to continually produce good work, are just the opposite. I will see a mid level team present their ideas (often same quality as the lesser agencies). Some are half baked, some are not- totally on brief, but you have a CD say “Wait a minute. Ok, go back to that one. What if instead of this part, we do this.” and will be able to turn it on its side and make everyone else see it from a different POV that makes it much better and strategically aligned. An idea that would’ve easily been dismissed at another agency.
When it comes to presenting, the agencies that produce the cool shit, usually work very hard to prove to the client that they have their best interest in mind, and that they’re not just trying to make some cool shit for their books. They try to keep the client’s eye on the target audience and the brand, and not on their own personal preferences. The account and strategy people work in favor of the creative and not against it. They let creative people work, instead of sabotaging them.
They have worked hard to generate a momentum where they have earned the client’s trust in smaller things, so that it carries over to the larger things too. It’s not an antagonistic relationship of the agency vs the client. It’s a relationship where the client and the agency are on the same team vs the client’s problem.
If the client can’t feel like the agency is on their side or they think that the agency has different interests than them, the agency starts at a disadvantage and the client always sees the work through a lens of suspicion, defaulting to the work they perceive as less risky.
What good agencies continually do is educate the client to understand that “safe” work is not very safe at all. It’s actually quite risky too. This liberates the client to be able to freely choose the best work and not just default to grabbing on to something perceived as safe— because now they know it’s not necessarily safer.
Another thing that is important to understand is the client’s needs. And I don’t mean the ones in the brief or the brand’s needs. I mean the person. When I say “the client” I mean “Sally from marketing”. What’s important for them? Is she trying to impress her boss? Is she just trying to just keep her job? Is she juggling 20 other things? How is she as a person? How much experience does she have? 20 years or 2? Does she have to present this internally to other people and try to sell it too? All of these factors are important in determining how you are going to approach your selling strategy.

So yeah, clients are a factor, but let’s not pretend agencies don’t continually shoot themselves in the foot and then play victim.

Present 2 good scripts.

Opposite ideas of what a “good” script looks like

For any idea to be liked & understood by any bigger group of people (for example your CD/ECD/CCO team + the client) it just needs to be as averagely interesting as possible.

As an industry we’re stuck to the limits of our understanding collectively. Unfortunately.

Never present anything to anyone that you don’t want to make, like ever

Watch Idiocracy and lots of stuff makes more sense

The toughest thing for me to wrap my head around as a young creative was how dumb the average audience is considered.

Always