Think about the timeframe. Then the tech.
30 years, but then complaints about T-shirts, vehicles and guns being the same as back then? And then complaints about the same environments as before, but looking too clean now?
Firstly, humanity isn't replacing the trusty T-shirt as a bit of easy and practical casual wear anytime soon. Complaints about the T-shirt are ridiculous, trying to replace a wheel. And only does it look good on old Deckard, it fits his no-frills character as well.
And vehicles? Honestly, where do you go from the flying cars they already had, barring faster, more efficient or automated iterations? That goes for their guns as well, again especially considering the given apparent timeframe for any possible advancements. 30 years.
A good gun design can often stay in service with an organization for decades, if it still continues to meet their evolving requirements, just tweaked and enhanced over time but the overall design may remain. Again, only 30 years here.
Then, you see those big-ass megastructures? Those're back from the original, right? Do you even realize what kind of arcana would need to happen in 30 years to renovate, refurbish, demolish and/or replace all of those COLOSSAL buildings? ESPECIALLY, with people still living and working inside them? The best that society could do with all that architectural baggage, in 30 years... is, surprise, clean it up as much as they can afford to.
Hence, fictionally-justified, the degree of missing "grime and filth". So apparently, by 2049 they tidied up their house; same city, just polished. But of course, the filth is still there, just buried. Hence, their need to still maintain the same order despite the change on the surface, as the problem causes haven't been addressed, just swept out of sight. Hence, Gosling's moving to uncover the old filth as the plot of this, bring it back to surface for us to see...
IMO, what we'll be seeing in Blade Runner 2049 is like a continuation of an '80s vision of the future, right? Cyberpunk... moving on.
You might say that the "grime and filth" was what made the world of Blade Runner feel "lived-in" and "iconic"; but again, time has passed where we're returning. Times have changed. Something about that old '80s cyberpunk vision of the future clashing with our current forecasts, which are based on the reality of the '10s. However, cyberpunk's high-tech-low-life is even more of an issue in our reality than it was back then, and I think we're going to be examining the cellular pager that is old cyberpunk, through the lens of the new smartphone, so to speak.
... /ramble