I haven't been told exactly that, but the first time I heard a tape recording of my speaking voice, I realised that I mumbled. I suppose mumbling and robotic are pretty much interchangeable terms for a lot of people. I had no idea I mumbled before I heard the tape, and I didn't like it. But after a few years I'd become better at the singing I'd started to try doing, which has a lot to do with intonation and word-clarity, and then a couple of people remarked that they'd never have thought from my speaking voice that I could sing so well. So here and there I started to try improving my speaking voice.
Just like I did to learn to sing better, I used sound recordings to get useful feedback about what I sound like to other people. Progress was quite slow for a while. I think it was something about poor confidence. And it was harder when I chose my own words and made it up without a script. I started to get somewhere when I switched to reading from books. I'd always liked reading aloud so that helped. A lot of it was about remembering to put intonation into what I said, and to use my mouth to better shape the syllables properly. Listening to professional book readers also helped. I admired the way some of them could command attention by the expert use of their voices, and I'm a born copycat. After many years, I happened to mention to a barber that I did a bit of live singing, and he said "I thought you might be a singer, because I noticed that when you speak, you project your voice better than most of my customers do." So I was quite pleased. I'm still prone to slip back into mumbling when I'm not feeling confident or when I forget to apply the corrections.
I think it's very useful socially to have a good speaking voice. People tend to quickly get bored with monotone, and personally I find it hard work listening to folks who mumble, so I guess I understand why it comes over as boring. So I think it's worth working on. I suppose a good way to learn would be to get on an acting course, though if that's too expensive or daunting, it's possible to make improvements without a engaging a teacher.