Desires, material and spiritual
Krishna fulfills everyone's desires, but He gives His devotees special treatment.
For example, if we want to become Krishna's devotees, but at the same time have material desires, He may fulfill our "not so spiritual" or mixed desires in a way we might not like—just to help us become free from that desire.
Or, if one is very sincere, He may overlook a "not so pure" desire and satisfy it in a roundabout way. If our desire is purely to serve Him, He will satisfy it to encourage and promote our service. But if it's tinged with false ego, he may nip it.
In other words, He will do what is necessary for the sincere devotees' advancement, knowing that the servant will accept His arrangement. He will try His best to correct and purify whatever inclinations we have that will hamper our devotional service.
Krishna also fulfills the desire of the nondevotee, even though it might not be for his spiritual good. He has granted us all a tiny bit of independence, and He honors our right to desire anything and everything.
There's no problem with worshiping Sri Lakshmi. Srila Prabhupada explained that when we worship Radha and Krishna with awe and reverence—according to strict standards—we actually worship Lakshmi-Narayana. Lakshmi is an expansion of Sri Radha. The problem—and the condemnation of the acharyas—comes when we worship Sri Lakshmiji in order to achieve some material prosperity.
Generally pictures of Sri Lakshmi depict her with coins coming from Her hands. She is considered the "goddess of wealth." Seeing Her this way, worshiping Her as a demigoddess, and asking Her for material wealth are all "condemned by the previous acharyas."
Sri Lakshmiji is the consort of Lord Narayana—She will bring us into His favor if we serve Her nicely—but if we ask Her for service, especially materialistic service, we're missing the point. The point of life is to worship Lord Krishna and go back to the spiritual world. The purpose of worship is to please the Person being worshiped—not to increase the material prosperity of the worshiper.