Which is why I just said "college players" the vast majority of which are playing tennis to get an education.
Any level rec player is not making money at the sport and therefore has no incentive to prioritize performance over health or cost. Fragile egos exist at all levels and are the prime driver for obsession.
Only important difference between a 3.0 and a 5.0 in equipment is how fast they break strings. A 3.0 with full poly will still be a 3.0. A 5.0 with full NG will still be a 5.0.
Or you can choose to believe that equipment doesn't matter and it all comes down to fitness. That will save you some experimentation and likely improve your game more. Believing too much in equipment is flawed viewpoint and its one that marketers are all too happy to exploit. "You hit that ball long because the strings and racket were too powerful!" No, you hit that ball long because you didn't get your footwork right and your unit turn in time and hit too much off the wrong foot. But racket and strings are easier to replace than footwork.
If you choose to believe you can play well with any racket and every bad game you have is entirely due to flaws in technique and conditioning, you will be well on your way to changing the right things.
Fooling with rackets and strings is fun but it shouldn't be an obsession.
As someone who has done a *ton* of experimenting with different strings (because of a sensitive elbow) to find a good mix of comfort and performance, I can say unequivocally that equipment is a huge factor in performance, especially at higher levels of even rec play. Is a bed of full poly going to turn a 3.0 player into a 5.0 player? No. But for me, a 5.0 player who hits a lot of spin in my game, playing with a full bed of poly vs. a full bed of multi or syngut can make a noticeable difference in my winners to unforced errors ratio. Tennis is a game of inches, and when a swing that sends a ball from a bed of syngut a foot long, brings the same ball down just inside the baseline from a full bed of poly, it is a big deal over the course of a match, or a league season. Your average rec player (even 5.0) doesn't hit 3,000 rpm on their strokes, though (even on their highest spin shots), and for them, the difference between a full bed of poly and a full bed of multi or syngut just isn't going to be as noticeable. I usually have a mix of stringjobs in my bag during a match. Recently I have been playing around with some Gut, Multi and Syngut set-ups (for benefit of my elbow), and I'll play the first set with one of those set-ups and just can't generate the kind of spin I need for my game and I'll be missing a lot of balls long. In the second set, I'll pick up one of my racquets with a full bed of poly in it and instantly notice a huge improvement in control, and spin, and the difficulty my opponent has dealing with my ball. It's not a placebo effect, believe me. I'm not saying pros aren't superstitious, a lot of them are (watching Nadal cycle through his OCD drives me crazy), but there is a performance difference between different types of equipment, and there can be a noticeable difference between the same equipment fresh off the stringer vs. when it's been played with for a few hours (or 7 games as with Federer).
I recently played a full match with a full bed of Prince Premier Control and compared my Playsight stats from that match against the match I played next week with the same racquet but a full bed of Prince Tour XP poly. On average, I was generating about 500-700 more rpm with the Tour XP than with the PPC. That is not an insignificant amount of spin, and has a big effect on performance at this level.
I can't play with full poly all the time, though, even at low tensions, so I'm still experimenting. Even Gut/Poly gives me a little soreness in my elbow sometimes. I'm currently in the early stages of trying out a Babolat Tonic/Tecnifibre Multifeel hybrid, because I was really impressed with how the mains snapped back every time on a full bed of MF, but a full bed wasn't durable for me. So far I've only got an hour on the Gut/MF hybrid, but the Gut mains are staying straight, I'm getting noticeably more spin than with a full bed of multi or syngut, it's pretty comfortable, and so far the MF crosses are showing more wear than the Gut mains. We'll see how long it lasts. It's not as much spin as Gut/Poly hybrid, but it's not *far* less.