Wrong.
The Xisha/Paracel Islands are located about 340 kilometers southeast of the closest major PLA bases on Hainan. From there, it's about 625 kilometers away to Huangyan/Scarborough Shoal to the east and about 750 kilometers away to the Nansha/Spratly Islands to the southeast.
View attachment 175025
Without Xisha, Sanya is about 1080 kilometers away from Nansha and is about 940 kilometers away from Huangyan. That's a massive distance to cover in one go - And we haven't talked about going south to Singapore (and the Malacca Strait/Sunda Strait).
In retrospect, Xisha basically acts like an extension of Sanya (and the Chinese mainland) by acting as a forward staging base for the PLA and CCG forces originating from Hainan and/or the mainland to refuel, resupply, and recuperate before proceeding to frontline bases and/or mission zones located further east, southeast, and south. In addition, Xisha is also capable of acting as a backup base in case something majorly terrible occurred at those frontline bases and/or mission zones, where immediate support/reinforcements are required. Xisha could be seen as a hub for cross-island travel for the PLA and CCG.
Furthermore, Xisha's location also means that PLA warplanes that are damaged during combat operations can have a relatively closer location to conduct emergency landings (and if that's not possible, ditching and be situated closer to rescue efforts). This is also essentially what Iwo Jima was back during the Pacific War.
Last-but-not-least - In case Huangyan and/or Nansha are lost, there's still the Xisha to fall back to. If Xisha is lost, then Sanya becomes the frontline.
So, no - The Xisha/Paracel Islands are actually just as equally important as the Nansha/Spratly Islands (if not some more).