Often clients don't understand what they want; like you say, the difference between met plonking in a basic combobox/select vs some much nicer, and much more fitting the case, custom ui element doesn't really translate to anything many people outside IT understand. To explain this difference it can be drawn, but stakeholders still don't understand what's going on as they don't see & feel it, so you have to make it work mostly.
I have clients asking 'just do the simplest thing you can do'; we present prototyped gui's then after approval fully designed guis and after that a prototype. They approve the first 2 immediately as they can't even be bothered looking at them; some, when pressed, will try the prototype and often still say 'yes great, let's go'. And then when it works and they can try it on the test server, they say 'no this is really not what we meant'. I have had this with 2 person mom and pop stores (long ago; I don't do those anymore luckily) to fortune 500 companies with the regional directors and global cto present to give their opinion. And this is frontend ... Backend, devops is another thing entirely, but there, is also a large difference between bare bones or gold plated.
I know the game by now, so these days we make a lot of money from this broken process.