WrestleMania is still one of the few times in the year that WWE matters, but it's definitely not this crazy spectacle that it used to be like.
A lot of that has to do with the buildup. Not every match needs to be treated like Austin/Rock II, but you need a reason to care. The matches need to feel like they can't happen anywhere else but WrestleMania. Undertaker and Shawn Michaels didn't need to face each other again, but they made you want to see it again. They worked their asses off to make the rematch mean something. It might not be as good as the first match, but it's just as memorable, and the buildup had a lot to do with that.
On the other side, you had Cena facing Rock again. They didn't need to face each other again, because them facing each other the first time was too big of a spectacle to even come close to surpassing. Not to mention the fact that it was way too obvious Cena was winning, there were better options for the main event (Punk vs Undertaker for the title, Rock vs Cena vs Punk in a triple threat), and the match itself was
. I guess WWE tried making you care, but it wasn't worth it.
Then you have potential WrestleMania matches on other PPVs, or ignored completely. Why did John Cena and AJ Styles have their blow off match at the Royal Rumble when WrestleMania was right there, when Cena going for his 16th title reign was a potential main event? I don't know. Instead, AJ faces Shane McMahon, Cena's in some pointless mixed tag match and the WWE Championship match we did get was bullshyt. Why did we get Triple H against Reigns at 32? Why did Reigns even have to lose the title twice before the match? Why not call an audible and put Ambrose in, or Lesnar, or both? Make the main event must-see so it means something when Reigns wins. WWE is so stubborn with their plans, they don't want to change anything, or they take away potential classic matches from us to get the plan they want.
Sometimes, they've gotten it right (Bryan being added to the main event, Rollins cashing in MITB, Bryan vs. Kofi at 35, Sasha vs Bianca). But for the most part, WrestleMania is something that will almost never be as good as it could potentially be. There's a reason we'll never see a show as well-booked and stacked as 17 again, because they won't allow it. Even a borderline classic Mania like 24 is too much for them to handle.