GC will not fix trashy programming. The problem is that many GC'd languages have adopted a style guide that commits to a lot of unnecessary allocations. For example, in Java, you can't parse an integer out of the middle of a string without allocating in-between. Ditto with lots of other common operations. Java has oodles of trashy choices. With auto-boxing, allocations are hidden. Without reified (let's say, type-specialized) generics, all the collection classes carry extra overhead for boxing values.

I write almost all of my code in Virgil these days. It is fully garbage-collected but nothing forces you into a trashy style. E.g. I use (and reuse) StringBuilders, DataReaders, and TextReaders that don't create unnecessary intermediate garbage. It makes a big difference.

Sometimes avoiding allocation means reusing a data structure and "resetting" or clearing its internal state to be empty. This works if you are careful about it. It's a nightmare if you are not careful about it.

I'm not going back to manual memory management, and I don't want to think about ownership. So GC.

edit: Java also highly discourages reimplementing common JDK functionality, but I've found building a customized datastructure that fits exactly my needs (e.g. an intrusive doubly-linked list) can work wonders for performance.