I recently read "All the light we cannot see." By Anthony Doerr. Lovely read. A sighted man describing what life is like from the perspective of a blind little girl. The summation is that life is fleeting and precious. It really doesn't matter what your "denomination" is. It doesn't matter what your belief in the afterlife is.
What matters is your connection to those around you now. What matters is your appreciation for the life you've been given. I resent people who try to attach a doctrine to someone else's viewpoint on this most precious gift, one that is unique to themselves.
I would take exception to your feeling that all is futile. With every breath we take, we move our existence and that of succeeding generations forward. Our experience, thoughts and viewpoints mold future generations to what humanity can hopefully become. Your thoughtful eulogy to the friend you've lost is a testament to the power of human kindness. My best to you at this most difficult time.....