On the Mahayana Vows

Aren't the Boddhisattva vows ("I will delay my own Buddha-hood and paranirvana until all sentient beings have themselves reached nirvana") impossible to fulfill?

This is to assume humans and sentient beings will live indefinitely.

Science tells us that's very much an improbable course.

That's not what I was saying.

Who says there is an finite number of sentient beings? Remember, Buddhism does not believe in an atman/soul: as such, the number of sentient beings does not decrease as more individuals reach nirvana.

If Buddha's teachings are correct and its simply human-level understanding that needs to change, then humans would eventually reach that same conclusion.

Other animals might evolve to reach human-level intelligence and reach similar conclusions.

Or the universe would end with heat death where all particles are separated and nothing holds together anymore, leaving no sentience being.

That's the point.

Yes, there are an infinite number of sentient beings and so boddhisattvas are eternally reincarnating

So for all effects and purposes, adherents of Mahayana Buddhism are vowing never to achieve nirvana?

>I will delay my own Buddha-hood and paranirvana until all sentient beings have themselves reached nirvana
What's even the point of such altruism from a Buddhist perspective?

No, they are vowing to liberate all sentient beings for all of eternity.

Yes, they place selfless compassion ahead of their own liberation.

As a Vaishnava and former Buddhist I think it's sort of foolish. The dharma will always be around if the age permits it and each person must ultimately figure it out for themselves. Thus the boddhisattvas are causing themselves needless suffering in my eyes, though I respect them nonetheless