To my mind, I know the game will finally be balanced when you can't just turtle to a win. It should be a requirement that you have to actually build an empire.
The problem is that this clashes directly with Civ5's wide vs. tall idea. Since "tall" empires do not want to expand, and since expansion is the only form of reversible conflict in Civ (wonder races are irreversible: once the wonder is built in a city, it cannot be relocated into a new one by "conquering" it), allowing tall empires to win with the same methods as wide empires enables "turtle to win".
For the record, I despise the idea of wide vs. tall in its current form, but since Firaxis does not, no Civ game in the near future will fix this problem.
I admit that it is a shame that a Tourism victory is so science-dependent, and this could be changed by not needing to have hotels, airports, NVC, Internet, etc.
It could also be changed by letting players generate a lot of tourism early on. The problem with Tourism is that it comes too late and in too small amounts before Internet and/or Airports + Hotels are both built. If tourism could be reliably generated in significant amounts starting from Classical, it would no longer be so tech-reliant. For example, Hotels' and Airports' tourism % would be reduced to 25%, but one new building would be added for Classical, Medieval, Renaissance, and Industrial Eras that would, among other things, give 25% tourism from culture; the fact that the bonus caps out to 150% of culture converted into tourism is intentional.
Making CV viable for multiplayer is a whole different can of worms: not only does the tech tree need to be tweaked so that Archaeology isn't so out of the way, but the whole idea of getting tourism bonuses from Open Borders and Trade Routes needs to be rethought, as human players will just deny you of these modifiers if they even suspect you might be going for CV. Trading Great Works must no longer be necessary to unlock any multipliers, seeing as players will not want to give you great works multipliers for free.
And I really disagree that they're all the same. DomV is completely different. You can finally ignore late-game science.
It kind of depends: unless you're Mongolia or Arabia or England with everyone coastal, you do often still need Dynamite as quickly as possible. If you cannot win with artillery, teching to Nanotechnology and Stealth is as necessary as Internet is for CV.