[WhitneyLand]

I think you are smart to consider your developer skills as a separate thing to improve. One way to objectively measure this might be to explain a technical concept to someone.

For example, could you read this article and then give an overview of the main issues of web site performance? Could you then come up with one recommendation for a performance improvement in a code base you're familiar with? Could you justify in practical terms why your recommendation was the best bang for the buck, vs. other other possible improvements? https://medium.baqend.com/building-a-shop-with-sub-second-pa...

Now, how do you judge yourself?

1). Have the conversation with a dev whose skills and opinion you trust.

2). Record your answers on audio, and ask someone on HN to give you fair and constructive feedback. Many here would be glad to do this (feel free to ping me as well).