The biggest problem I see cropping up in these comments is personal preference.

Let's take the example of cutting across two parking lots separated by a strip of grass. Not picking on you at all Artkansas, just that it illustrates pitfalls that Google is going to have to avoid. I take routes like that all the time - I prefer routes like that! But not everyone does.

1) Your route takes you across private property. That's a big legal pitfall for Google

2) Your route takes you through parking lots. A LOT of people on this forum would rightly call a parking lot a death trap. I can see you responding "oh, those parking lots are always empty" or "one is a police parking lot so I feel safe". That may well be true but how is Google to really evaluate that? They could go and look, stake it out, etc. but that's no scalable. How do you do that with hundreds of thousands of parking lots?

3) What's the nature of that grass strip? What if there's a lot of rocks? "Oh, it's not that bad" - how is Google to evaluate that? What if you ride an MTB? What if you ride a Cervelo with Zipp wheels and silk tubulars? What if you ride something in between? What if it's a goathead patch? "Oh, if you run <tire X> it's not a problem" - what if you don't? What are the entrances and exits to that patch like? "You can just bunnyhop the curbs" - is that a viable option for everyone? What happens when it rains? Does it get super muddy? "When it rains I take a different route" - how do you illustrate that with turn-by-turn directions?

A couple of other examples:

"Suggested I ride down a very narrow, steep road with zero shoulders...one I would never consider riding down." DOWN? I'd ride down that! Up? Maybe not!

"It missed a pedestrian underpass under a busy street". There are a lot of folks on this forum who ain't gonna ride "pedestrian" nothin' - including MUPs

My commute has a section that's been closed for several months. It's slated to open back up next month. It's easy to bypass by riding across 5 or 6 fairly level yards which is what I do. How should Google list it?

Realize that (as I said) this service is intended to get you to a place you haven't been - or at least a ride you haven't been on. They need to find a RELIABLE route they can put people on with confidence. Will this always be the fastest route? No. The safest? No. The shortest? No. Should they put on shortcuts that could get shut down any day? No. Should they put on routes that are weather dependent? No. Should they put on routes that depend on putting on a sprint a few yards early to insure you outrun the loose junkyard pitbull that lives along it? No.

They'll never be able to calculate routes that are 100% optimal for every rider every time of year. It's just impossible. I'm not saying that it's perfect as it sits by a long shot. But if I tell them about the shortcut I use by cutting across a trash-strewn vacant lot and ducking through the hole in the fence should they put that in their database? Heck no! We'll make there job a lot easier if we self-evaluate the changes we suggest beforehand. Which would be a worse failure for Google - "It missed three shortcuts" or "I got a million goatheads in my tire" or "there was a 6 foot fence blocking Google's route and I had to backtrack a mile and got lost for half the day and got mugged and bitten by a pitbull?".