Pupette

Of course everyone is allowed. Opinions are the source of a good discussion, specially when they oppose each other. You don't like the white spacing as it is, it is a perfectly reasonable opinion. I like it and i think this theme is a nice improvement over the previous one - also a perfecly reasonable opinion.
Now, i wouldn't like the white spacing to be reversed or shrunk. First, because i my opinion is exactly opposite (fair enough, i guess 😄 ), and second, because there is not any objective data to support the opinion that shrinking the white space would improve the interaction.
 
Yes, but Google also frowns on content being too close to each other in mobile, for example. There is always a compromise that needs to be achieved...

I see too much criticism here for the theme and the white space. UX is always a matter of discussion, and everyone has its personal tastes. Now try to put personal tastes aside, because everyone has his own ones.
Do you have any UX test metrics other than "i don't like it" to present to support your views?
My opinion is, this new theme is  great improvement over the previous one. Is it perfect? No, specially mobile-wise topic page navigation (you have to completely scroll down or up to move to next page, which is not user friendly, for example - surely this can be measured) but regarding the white space, i like it. It helps the text to "breath", and allow better reading. It doesn't bother me at all. My personal taste here, as valuable as anyone's.
This is not a challenge of "how much content can be put in the screen". Simplicity is beautiful. Crowded interfaces confuse users.
Thumbs up for the overall improvements that the IPS has put in the 4.5 theme. I could not use the 4.x theme directly without customizations, but 4.5 theme is good enough for it.

Rikki just answered you and dealt with it extremely well by answering your question and did listen and explained why. One reason I've been with IPB for this many years is because of their open design instead of bunching everything too close. this isn't the 1990's. 
Just because you don't like something doesn't mean it needs fixed. Obviously by Rikkis answer it's WAI.
 
Yes we do, and I think it's just fine and so do many many others.
Have a nice day

In 4.5 we've tried to keep headers consistent, so that buttons are where you expect them to be, there's space for additional buttons as each page/app might require, and so that each page/app can extend the data shown in the header without the whole thing breaking down. In 4.4, this was a problem - sure, on perfect example pages, the follow button worked well in the top right. But using a different app where more buttons need to be shown, or even just having a long topic title, suddenly it wasn't so pretty and usable. The new header is designed to be flexible and extensible according to requirements.
It's pretty easy to take one particular page and find criticisms - but remember we are designing a suite where each page might have some shared functionality and some unique functionality. We have to design components that can work well in more than one perfect scenario. 

The problem is that every update breaks our customizations. I am tired of this never-ending cycle of chasing a moving target. The default skin is finally good enough I feel okay just replacing the header and footer with our own. So in spite of my criticism, things actually are moving in the right direction.
I don't think it is possible to ever get the skin perfect:
Google is forcing everyone to use "responsive design" which massively complicates everything. If we had a free-market economic system the government would shut down monopolistic practices like this, but I digress. IPB is a collection of applications with some shared functionality, and that modularity of features will always lead to some tricky design choices. So I think we can reasonably expect to see some awkward spacing in various parts of the design. However, I think some more effort should be put into improving the most common parts of the most commonly used functionality, and the forum topics list is probably one of the top three pages that get viewed most frequently in the software.

you can't
There is a big thing missing on Classified apps :
1) the possibility to filter the results : by price, by brand etc
2) A real search box with multiple criterias like you can see on various marketplaces :
i want to see the adverts with price less than $100, belonging to a category in particular etc
This is the major improvement we need for Classifieds
PLEASE LIKE THIS POST IF YOU SUPPORT THIS REQUEST !