Rim wear is a difficult area, you want to replace the rim a few minutes before catastrophic failure but how to tell when it's about to occur is tricky. The most spectacular example of brake pad wear induced failure was whe a colleague of mine was pumping up a Brompton wheel off the bike with a track pump. He got close to the recommended pressure when the whole side of the rim flew off with a bang and flew across the room. Quite spectacular but not the kind of thing you want to happen on a fast corner surrounded by traffic.
Brake wear can be influenced by many factors, the most common cause of accelerated wear is when brake blocks are used for too long. Over a period of time the surface of the block will pick up bits of grit and specks of aloonyman from the surface of the rim. These, now super abrasive, blocks will devour the brake track in a matter of a few weeks. Dirty bikes are more likely to suffer from this. The very worst thing you can do to a rim is leave the brake blocks to wear down to the steel backing plate. OW!! That desperate scraping noise is the rim dying.
Old blocks with some life left in them can be made rim safe by being sanded or filed down. Lay the file on a bench and run the block flat on to keep the surface nice and even. Clearly its much cheaper to replace blocks than to replace rims or complete wheels.
Entry level bikes are more likely to suffer premature rim wear because they use cheaper aloonyman. Small wheeled bikes suffer because theres less material there to wear out. Bromptons seem to suffer because their owners often dont clean them, they ride around for ever with a lovely abrasive soup on the rims and are taken by surprise when their rims fail.
Brake wear indicator tracks are a mixed blessing, most people dont know they are there for a start but in my view cutting a groove into the brake track is simply removing material from where you actually need it most.
So to sum up, keep your wheels clean, resurface or replace your blocks regularly and when replacing rims get the best that you can afford. Hard anodised (or even ceramic coating, yum) lasts very much longer than cheapo 2000 series aluminum.
In answer to the OP. I dont know if your rim is worn out because I cant see it. Sorry. Your LBS will tell you.