Well, spiritual is being connected to something you can't see or touch, and have no proof of its existence, but that you somehow feel. Thanos' love for Death was quite palpable, as she was an actual cosmic entity that is part of Marvel's cosmic mythos, somewhat similar to H.P. Lovecraft's Outer Gods, or Great Old Ones. Reading The Thanos Quest, I always felt that his motivations were quite selfish, and Adam Warlock was the only one who could really understand and call him on it. I still think it's an absolute sin to not have Adam Warlock in Infinity War.
Kevin Feige is mucking this up big time.