With all of this talk about footwork I thought that I'd share a thought..
My sparring was always held back by my poor footwork. It wasn't until I learned swordsmanship that I was able to improve. In swordsmanship one must always threaten the opponent with something in order to advance, or eat their sword between steps, which is a vulnerable time. Some good examples can be seen in the below video at 08:35 and 9:50 (and in slow-motion shortly thereafter):
https://www.youtube.com/watch?v=QFe_SiCXlUk
In the first example I accidentally hit the ground on the way in, but in battle that can happen and I still would have won the exchange with a broken tip. One exchange is usually all it takes. Note the footwork, though. In both examples I threatened my opponent and charged in to close the distance and land my strike. With unarmed fighting it is the same. Whenever one wants to advance the rear foot, the hands have to be doing something to threaten the opponent. A good example can be seen in the video below at 02:33:
https://www.youtube.com/watch?v=Pb94tMqpn84
Nowadays I use a lot more of this type of footwork both in armed and unarmed fighting. It helped me to improve my Shuaibeishou a lot. I had the power, but I wasn't always able to hit my target. It works great with wrestling too, where it is perhaps even more important in closing the gap, but there isn't really the danger of eating a punch on the way in, so what I was saying before doesn't apply as much in that context.
In an art like Tongbiquan, though, it just doesn't work without this footwork and I believe that that is where practitioners fail to really make use of their art. That and not training to make the strikes really heavy like the ones in my example in the video above. My student already knew what I was going to do, so he kept running away (wisely). In actual sparring I would explosively pursue him and then switch to something else to throw him off. Only by advancing my rear foot can I pull that off.
In conclusion, I believe that being able to advance the rear foot is one of the most important signs that someone can use their CMA skills in sparring. I hope that I was able to type my thoughts concisely enough for you to understand. Keep training hard. Don't be lazy!