It feels low right now but I don't think it's a horrible deal from Robertson's perspective. On a 8 year deal he'd probably get what, $9mil-ish? Maybe a little more maybe a little less. That would then mean his next contract comes up when he's 31 years old.
This deal comes with an AAV slightly lower than the deals Kyrou and Thomas signed recently, but they got 8 year terms. Robertson will be able to sign his next deal at 26 years old where he could either do a one-and-done to hit unrestricted free agency at 27 or just do a massive 8 year deal when the salary cap could be something like $95mil.
I've never really understood elite players signing 8 year deals in their early-to-mid 20s. Obviously you can't discount the security that provides but barring career ending injuries it always seems to make more sense to go this route (as Matthews somewhat did too).