I wouldn’t say that I’m good at lucid dreaming as in having them at will or with high frequency. But that doesn’t mean I can’t enjoy them 
I’m also over 30 and as I approached my late twenties I also thought that having lucid dreams will only get more difficult from then on because they were indeed getting rarer and that’s what many websites say. Now I don’t believe that anymore. I’ve had about as many lucid dreams this year alone as in my entire previous life. So please don’t feel discouraged because you’re not a teenager anymore or you started too late.
It sounds like your fundamentals are indeed solid. When you do WBTB, what does that look like? Do you do any induction technique like MILD or WILD when going back to sleep?
About your lucid dreams, when do they happen: only during the last sleeping phase or also in the middle of the night and sometimes before your WBTB?
Now how to improve your chances at LDs and making them longer, if forum member @Rhewin was here he’d say it’s all about awareness. And I strongly second that. It seems like a suitable solution to your situation. Have a look at this tutorial written by him:
How does this resound with your experience? Are you really aware in waking life? In a nutshell: If you’re not lucid when awake, trying to be lucid when asleep is a dubious endeavor 