VMA doesn't solve a lot of hard problems around memory management, which really come from synchronization issues. You need to make sure that the GPU is done with a resource before you can destroy it on the CPU side. What it brings is a host of allocation algorithms for very specific use cases and a lot of code for tracing/debugging memory usage. Plus, it shields the users from some positively braindead quirks that the Vulkan spec has gathered (some through extensions that create traps when they aren't enabled - just present; I had to scream when I pieced that together...).

I have my own slightly anemic memory manager code that implements a basic scheme with no frills, avoids pitfalls and fits into about 500 lines of code. The only thing I really might want to improve is the some of the free lost handling. The rest shoukd be good for quite a while.