Because I believe that the base bonus is no longer exist

Yes I am Platinum 3, and today I received less than $25 on the monthly bonus.
My VIP rank is also Platinum 3 and I got the same amount like you. My wagering activity is quite low within last 30 days period. My PnL statistic is negative (less than $100) with only $6k wager. So, I won't complain about the amount this time.

Maybe this is not enough to prove that there is no base bonus anymore or maybe there is higher minimum wager requirement within a month in order to get the bonus?
They still have a base bonus amount, but it has been reduced significantly. Perhaps, the base bonus amount is between $10 to $15 for Platinum VIP rank. We have to wager a certain amount in order to receive the base amount. Then the further wager increases our total bonus amount. The effective percentage of the house edge and PnL contributions is unknown though.