There kinda-of is. That's the beauty of the games that have become 'true' classics.
As per the UK Open, you can make *any* pin harder, and really good games 'open up' as you become a better player.
AFM draws in the punters with the excitement of the first saucer, but - then - there are lots of things to go for after that. And, with hungry outlanes and lots of wax on that open playfield, it's not something most players can simply 'finish' and be done with.
I appreciate that some people do get bored when they 'finish' a pin, but pins aren't video games - they're physical objects. They should provide kinetic satisfaction by being fun to shoot, regardless of your ability level.
We have JP2 and TNA here and I'm only reaching paddock 2 most games, and TNA has probably the shortest gameplay loop of a modern pin, but they're super-fun to shoot regardless.
On D&D, I think it would be weird if the pin didn't have a levelling-up mechanic - it's a core part of the theme - but I worry there's a tendency among pinball manufacturers to try to cater for home buyers who turn every new pin to 5 balls, narrow outlanes, bang-bang-finished-the-code, bored now, now onto-the-next-pin, and, if they can't do that instantly, it's a bad machine.
They're the people who the 'grinding' mechanic is for, but for me personally, that's not what makes pinball fun.