How does Buddhism provide a foundation for morality and ethics without devotion to a personal God or divine authority?

I came across a Vaishnava critique of Buddhism which questions whether Buddhist ethics can have a stable foundation without having the concept of devotion to a supreme God. Quoting the excerpt from here > **what is the problem with Buddhism?** > > Before the advent of Sri Shankara Acharya, Lord Buddha (Sriman > nArAyaNa Himself on the authority of srimad BhAgavata PurANa) has > given an illusory theory for the people of material consciousness and > made them adharmic with His excellent philosophy (Lord is beyond our > perception and His actions are in-conceivable without guidant of > Acharyas). He gave a philosophy based on moral laws, athiesm, denial > of vedas and illusory "nirvANa(viodness)". His instructions are somuch > attractive that any person who is not adherant to vedas and devotion > unto the Lord gets easily carried away. He lures unintelligent men by > saying only intelligent men can understand His philosophy. That > enables people not to investigate His philosophy critically and > accept. Moreover, on the surface, one cannot find fault as it is based > on moral laws like non-violence and truthfulness. Even today many > people think philonthropic actions and being good is ultimate purpose > of life. But they miss the critical point why should one do either > philonthropic or good works. They have no clue what actual good is. > The purpose of all good actions is to attract the attention of the > Lord and get pure devotion unto Him. > > When we do not develop love for the Supreme Lord, we lose all our > morals and dharma at some point or the other. We are never independant > of Him. As we can see today, in countries like china, people lost > their own religion, forgot all good (their own moral laws), consume > more meat (including frogs and snakes) than any other country, and > work day and night like machines to improve material comforts. This > proves, how it is most important to have mercy of the Lord for the > living entity to have ethical life and subsequent desire for eternal > bliss (liberation). Lord doesnot allow selfish people to serve Him, > for He accepts only unselfish, unbroken devotional service. We should > know from this example that acting in all good ways is only to develop > love for the Lord. According to this critique, without divine guidance and devotion, ethical conduct eventually collapses, and moral laws lose their meaning. How would Buddhists respond to this critique and provide a solid basis for morality and ethical behavior within their philosophical framework, given that Buddhism does not ground ethics in pleasing or serving a personal God?