Why is the Kingdom protista and the five kingdom system consider obsolete?

Kingdom protista is for the most part used for convenience rather than to provide scientific value. It was created to put any eukaryotic life form other than Plants and Animals in it. It is the most varied kingdom of all and there are no signs of a common ancestor between any of its members, they are all just dumped in there and clified accordingly. As for the five kingdom system being obsolete, I would not bet on it. This kingdom system has always been changing from the original Plants and Animals to the Prokaryotes and Eukaryotes, to three, five, and six divisions. I do not see it as being obsolete for the moment, everything fits snuggly.