There is no set time or even guess that it'll take to be a skilled fighter. I've sparred guys who had never sparred before and had them say "Wow you're really good at this" and I've just said "Yeah you're going to be better" because you can see talent like that (The guy that springs to mind when I said that is now something like 45 fights and 36 wins into his career in Muay Thai) and I can tell you right now. I had over a decade more training and experience than him and I wouldn't want to fight him now because he would beat the absolute fuck out of me.
It really comes down to your natural ability and I'm not just talking about fighting. Some people are natural fighters, but to become a skilled fighter you need the ability to want to learn and take lessons onboard and I mean genuinely not just saying "yeah I want to be a fighter" but you don't really learn because you have a mindset that you already know what you should be learning (
@ironkhan57 springs to mind).
You need the ability to be able to adapt, the ability to stay calm under pressure, the ability to fight your flight or fight instincts and then a whole host of other little things that might seem somewhat inconsequential but in the long term form who you are and how far you can go with fighting or how skilled you can become.
I was a good fighter, not to toot my own horn but I knew how to win and didn't worry about looking good to do it. But I never had the skillset or the mindset to stand out or go anywhere with it. I'd still back myself any day of the week over 99% of people on this forum in a fight and that's because I know I'm more than likely better than them at fighting, I spent 18 years competing as an amateur and as a pro before a hand injury that took years to heal ended that chapter of my life. But I also know that at the end of the day I was never going to be a world champion or any of that shit, the people that make it there have levels of dedication and belief that I never had and honestly probably could never have.
So don't set out with the focus of becoming a skilled fighter. Set out with the focus to truly learn and take on board what you're taught. Even when you think you know better or know it all, you can still learn. My problem was I never wanted to learn, I just wanted to fight. I had coaches that didn't even try to teach me because they knew I wasn't going to listen they just guided me with tips and gave me advice if I asked for it. I had coaches that taught me a great deal because I wanted to learn from them.
Learn and discover what you become.