It's been a little hit and miss since the attitude era. From 2002 up until around 2005 it was pretty solid, but then it kind of sank into the PG style of stuff and you had a lot of crud. Nowadays is probably the best time to jump back in. There are still a few older guys around but most of the talent now are the younger guys who came up in the last couple of years who are some of the best guys to watch. Actually the current WWE Champion, Seth Rollins, only debuted back in 2012.
But yeah, the event is looking pretty solid. The main event is Undertaker vs. Brock Lesnar in a re-match from Wrestlemania 30 when Lesnar broke the streak. That alone makes it worth watching.
Theoretically, the outcome of the Undertaker/Lesnar match should be a no-brainer. You mentioned the older guys and the Undertaker is 50 years old. Lesnar is 12 years younger and a very tough customer. Brock Lesnar is also his real name, which is extremely rare in the wrestling business. Of course, wrestling being what it is, match outcomes are tough to predict. It all comes down to the story line and how the match is staged. Whoever wins, you can bet it will lead to more hype about a rematch at the next Wrestlemania or whatever, to keep the fans coming back. The match I'm most interested in is Cena vs. Rollins for the WWE and US titles.
Another potentially interesting event is on NXT the night before Summerslam. Finn Balor is defending his NXT championship against Kevin Owens.