How sound is the understanding that the non-response to supplication may be due to having a poor opinion of Allah, especially since Allah has promised to answer the prayer of the supplicant and that the answer to supplication comes in one of three possibilities? And does this understanding contradict the texts of the Qur’an and Sunnah?

"To fulfill supplication, there are conditions and causes. And 'except to worship Me' does not mean confining worship to supplication, but rather supplication is the greatest form of worship. The answer to supplication includes three forms: fulfilling the request, saving it for the hereafter, or averting evil. And having a good opinion does not mean hastening the answer in this worldly life, for Allah may delay it out of mercy for His servant. An example of this is the supplication of the Prophet, peace and blessings be upon him, whose answer was delayed in some instances."