A professor commented that my research is too simple as compared to my colleagues. What does that mean about my future prospects? I gave a departmental seminar yesterday. It was a short 20 minutes presentation of my PhD thesis. I had presented two of my published works during the seminar. My research topic was to model an experimental manufacturing techniques. I have published two papers (in decent journals) and will be submitting few more. 

One of my departmental senior professors privately told me that I am doing too simple research as compared to my labmates. 

I know that I am an underperformer in my group, but I never thought my research to be simple. Now, I am worried how my research will be perceived by prospective future advisors and faculties. My advisor says not to heed to the professors comments and that I have done a good job. However, deep down, I feel that the professor might have a fair point. I don't know what can I do now. I have already submitted my thesis and will be defending in couple of weeks, though that professor won't be in my committee.
Perhaps the best route is to split the difference. Note the concern of one professor, but take heart from the support of your advisor. There are a lot of possible explanations. 

Perhaps the professor making the comment is overlooking some aspects that are harder than they think. Some things that look easy from the outside are harder when you get into the details. And, perhaps, that professor is just so brilliant that the crux of your problem seems obvious to them. There are such people, of course. 

Perhaps your current research really is simpler than that of others in their circle. But you are still early in the profession. You will probably do better work as you advance. The dissertation shouldn't be viewed as your life's best work, only the first. 

There is no real reason to worry at this point, and certainly not to panic. But long term, consider the advice you were given. Perhaps a bit more experience will help you judge its merits or lack.