It's been two years since Salesforce launched LWC and looks like salesforce is not going to slow down.

If you want to ramp up your skill in Salesforce Lightning Experience Development then for sure you would have to consider the thought of learning JavaScript?

JavaScript community evolved rapidly ever since ES6 is launched. Lot's of new concepts were introduced, helper methods were made available, you can think of it as a new framework altogether when you compare it with the old JavaScript.

There are a lot of modern JavaScript frameworks that are built on top of ES6. ReactJs, VueJs are the most popular frameworks among a few other frameworks.

LWC is also built on top of ES6 and my personal opinion is LWC is heavily inspired by ReactJs and VueJs.

If you want to master LWC I would say it's a mandate to learn ES6 first. Do not make the mistake of jumping directly on to LWC, the learning curve might be a bit steep and if something goes wrong you might even drop the idea of learning it, midway.

So, my advice would be start of with JavaScript and then jump on to Lightning Web Components. To help you get started I have created a FREE course on JavaScript.

You can get access to it here.

If you have time I would suggest you learn any one of the 2 JavaScript frameworks(ReactJs or VueJs).