I believe it is yes and no. I agree with NoBadMojo in that the better the player, the less the racquet matters. Once your strokes are grooved, a good player will adjust. Let me give you an example. I am an ex college player and experiment with racquets a fair amount and try different ones all the time. I estimate within a few minutes I can play to 80-85% of my potential with almost any racquet I pickup. I am sure most advanced players can do the same. Will we play to our potential that fast? Not unless the racquet is close to what we use normally. So the real question is who are we playing with and the situation? If I am playing social tennis or casual tennis, it doesn't make much difference. But you start playing the best players you know or a serious tourney and then a switch will make a difference. Because the the last 10-15% (usually less than that) can make the difference between winning and losing. You might not pull off that specialty shot or running up the line passing shot you like so much because whatever you are playing with probably doesn't feel the same as your usual stick. You probably won't play your best until you adjust. Which may never happen depending on the racquet and your preferences. Who knows.
If you are learning the game or are say a 3.0, I think the racquet makes more difference. No offense intended for anyone as we have all been there. If your strokes are not as grooved or you are out of position when you hit a shot, the racquet will make a big difference in the outcome. When we are learning we just can't adjust to things that fast. We are too busy just trying to hit the ball in the court let alone have time to think about our racquet. So if you give that player who wants to try his buddie's k90 tour, he/she will probably not like it. Give him something his retired father uses that is super light and super stiff and he will probably not like that either. Sure he can play with either but it will take quite a bit of adjustment and it will take him/her longer to play to their potential when they switch.
So the bottom line I guess is yes and no. We all play to our potential with certain racquets or types of racquets, whatever type of player we are.
Good tennis to all.
TM