I'm disappointed in the lack of the subways ... BUT, I'm understanding, and accepting of it.
Additionally, even if CDPR never ever puts the subways back into the game as a working thing, I kinda have some hopes that the game will have LESS RESTRICTIVE MODDING support in the future.
Why is less restrictive, to full-open-unrestricted modding important?
The Modding Community, given the access and tools, is the Jesus you didn't know you needed, and will not only save your soul from subjective preference frustrations, but, can "save" the game.
With Open-Unrestricted Modding support, modders can, and will add those subways.
Modders will enable Mantis Blade Wall-Climbing too.
You'll get more desctructable environments, new animations, new idles, new textures, 16,497 different clothing options, new apartments, base-building, companions, new quests of various quality, new cars, new paintjobs for cars maybe even auto-shops for immersive paint-job changes, 3rd Person Perspective (already a mod in existence, but, it's silly with the restricted access), new character skeleton models that have more clothing slots for jewelry leggings and much more, new kinds and types of cyberware with appearance changing effects, entirely new quickhacks ... and just so very MUCH more.
Modders, given open-unrestricted modding access will also do tons and tons of really stupid and ridiculous things, but, if having a flying Tommy the Tank Engine come pick you up and fly you around the city is your thing, someone will certainly make that possible. If having boobs so big they clip through the windscreen of your car is your thing, someone will make that possible.
Everything you never knew you wanted or needed, and lots that you don't and won't want, modders ... given open, unrestricted modding support, can provide.
Modders gonna mod.
We do NOT, however, have that level of access right now.
It's not stopping the community from making efforts, creating "Better Driving" solutions, "Walk Toggle", "Dedicated Dodge", some clothing replacers, and some aesthetic appearance things ... but, there's only so much can be done.
That 3rd Person Perspective Mod, for instance ... works ... kinda, but, your character looks like some weirdo blobby squishy rubbery thing without bones. Some less restrictive access for modding could fix that and make something actually presentable.
There's a live-reflection mod too. You can see your reflection and reflections of all the things in anything that's reflective ... except, when you look at yourself, you got NO head. That can be fixed with less restrictive modding. You could have changing rooms at clothing shops where you try things on and have live mirrors to see how well you can rock ... whatever style you choose.
... and, as far as shops go, they could get got modded too to actually act like real stores with specific, stable, predictable lines of clothing so it's less random, with bigger selections, but, select shops could offer Bespoke Custom Tailoring which could be an immersive mechanic for elevating the rarity of clothing items at a price ... even up to Legendary with full slots.
Same goes for gujn shops.
I could go on with ideas for selling cars you have but don't need/want to used car shops for some extra eddies, pawn shops for items you can do without or can't use because you're too low level, but, you want to keep them and could use the cash for putting them in hock to buy back later ... and much more, but, in the end, there's a ton of things Modders COULD do ... like the trains, BUT, we don't have open-unrestricted modding support.
Will we get that support? Maybe, but, i suspect not. We never got that level of access for The Witcher 3, so, evidence would indicate what we have is what we will always have, and, that's a little sad.