Yes. It’s not that we can’t build them, like obviously we could if we really wanted to. But the techniques (both in terms of construction detailing/design and the actual, physical construction techniques of assembly) used to build them are not practiced anymore. You can produce buildings that look very similar, but won’t be identical. For instance, let’s build your 4 story brick tenement—back then they’d be built using solid masonry construction and wood framed flooring. Not flying today. Breakdown of why:

1.) You would not find many, if any, contractors skilled enough in building multistory buildings with solid brick walls and wood framed floors. More likely you will have a brick rain screen (1 layer of brick) supported on walls framed either in CMU block or metal stud framing. Already this will lead to a difference in the way the detailing in the brick facade is expressed. It becomes more economical and controllable to use pre-assembled brick masonry panels that are then installed on the facade on-site. Instead of wood framed floors, you will have concrete slab floors, which also ends up affecting the overall detailing, and therefore architectural resolution, of the building.

2.) Those ornaments you see on prewar buildings were once mass-produced believe it or not. For more upmarket or higher budget buildings, industries of masons and craftspeople existed that created ornament per architectural drawings. No longer. Custom ornament is expensive, which is why on so many “new classical” buildings you’ll see ornamental figures that are reminiscent of the ornament seen on older buildings, but with much flatter profiles and lower resolution. Example: compare the street-level facade of Carnegie hall tower with that of its namesake neighbor.Probably a bad example since it’s behind scaffolding right now but you can Google it.

So, in aggregate all of these factors (and more) mean that you can’t really make buildings that look pre-war, let’s say, without going through a lot of expense. They’re viable as one-offs, for big-budgeted institutions. And there are many “new classical” or “new traditional” buildings going up all over the place–but to any trained architect, and probably to anyone with a little aesthetic sense, all but the most carefully-made ones look REALLY BAD.

That’s why I don’t think it’s worth rebuilding Penn station to its exact historic design. It’s sort of papering over the palimpsestual process that is city-making. The act of it’s destruction is so integral to the foundational myth of late-20th century New York that to me, rebuilding it outright would almost feel stranger than preserving its memory with something new.