Well, compared to stake.com support, which we all know is managed by the same team, stake.com's customer support is not as good compared to primedice. It takes much more time compared to primedice, maybe because stake.com has more players and problems than primedice.
Yep, the delays in response are related to the more support inquiries from the users. I just checked my last 7-8 chat history with the support agent of both platforms. Primedice support always replied to me within 1 to 5 minutes, where it took at least 5 minutes to get a response from Stake support agent in most of the time.
Stake has more support member than Primedice, but they have thousands of more games and sportsbook which brings more support related inquiries. Moreover, Stake online users count always remain 150× to 300× of Primedice average active users. So, it is reasonable to have more questions from the user at Stake than Primedice.