I reported this 2 months ago. Nothing has been done by our city.

Being fairly new in the neighborhood, I'd like to hear from people living in the area: do you think the situation has become better or worse over the years and what do you think is the main cause?

The situation has become much worse. Looking at 2011 street shots of some of what are now the worst spots in the neighborhood, there was no trash, or very little. You could have cleaned up West Oakland with a single dump truck. Not today! You would need a fleet of dump trucks and dozens of workers.
As far as the cause, it is three-fold:
1. No enforcement by the city (police, code enforcement, city attorney, city council, mayor, etc.)
2. Haulers and contractors who take advantage of No. 1 to dump their debris here (free!) instead of at the dump (costly).
3. Alliance Metals, the roll-your-stolen-cart-up-and-get-your-daily-drug/alcohol-money business.

Thank you Betty.
These streets are by far the dirtiest I have seen.
(Even the poor countries I have visited have at least some pride in the little they own and try to make the best of everything. Here it is the opposite!)

It looks like relocating the recycling centers are a priority then.
And hopefully keeping reporting on SCF will make a change too.

What has made it worse is the "Artist" who is making the mobile little houses. Instead of being in empty lots (like areas under the freeway overpass at the end of Mandela) the homeless have now parked these miniature houses on the sidewalk and they quickly become surrounded by human waste, junk, and other trash. I have also seen prostitutes operating out of them.

The City needs to order the artist building those to stop or charge him with illegal dumping. His good intentions are not good for the majority of the neighborhood.

I would say that in general, things are much better than a decade when my family moved to this neighborhood. There are issues that always pop up such as the City Slickers Gazebo Fiasco & now the miniature homes, but the local community bands together to solve the problems.