Is love in the 21st century something different than what it was in the 20th, or before that? Will it change as we move forward with time?

It’s only our perception of it which is constantly updated, changed or challenged. It might be difficult to explain, or it is actually fairly simply which is over-thought and overdone. If I have to put it:

love  /ləv/

Noun
An intense feeling of deep affection: “their love for their country”.

Verb
Feel a deep romantic or sexual attachment to (someone): “do you love me?”.

Synonyms

noun.  affection – fondness – darling – passion
verb.  like – be fond of – fancy – adore