Sexton is not typically the most "fun" player to watch, because he often plays it very safe and does not take wild routes or run risky longer putts. However, if you're watching with an eye for shot selection and course management, he is very entertaining to watch. I also appreciate that he has good BH and FH, and that he's very willing to use either in a lot of different situations.
A related thing about Sexton's game, is that he throws almost excusively straight, straight-to-fade, and just pure hyzer lines. He is able to work flex shots and turnovers, but you can tell his preference is to take simpler lines that are higher percentage. Because he has both accuracy and distance for both FH and BH, he has the options to play hyzer-ish type lines on pretty much any fairway shape. So again, you don't see the big flashy hyzer-flip-to-fade triple S-curve shots. What you do see is a lot of variety in technique that all leads to one common result: consistent, safe, well-placed throws.
That's why you see him excel at courses that have a lot of technical challenges, rather than just pure distance. I don't think I'd put him in the very top elite tier of players that are near the top for every tournament. (You know the guys: Paul, Eagle & Simon this year, and I suppose Ricky "Foot Fault" Wysocki has to be on the list.) But there's certainly a class of courses where Sexton is frequently in contention. (And those courses are often more fun to watch!)
Also, as others have pointed out, the guy is just a real class act and a great ambassador for the sport. Always very professional but also fun, he's a good communicator and probably my very favorite disc golf commentator. Also he's a family man, which I think is a very positive image for the sport and sadly it's too rare among the top touring talent. The Sexton brand is expanding: signature CG Firebirds, Sexton Shootout, signature Grip6 belts, signature Octothrope. Overall I think Nate's going to be a force in the pro disc golf community for a long time.