I think I know what "I love you" means.

"Dark Sonnet" by Neil Gaiman

I don’t think that I’ve been in love as such
although I liked a few folk pretty well
Love must be vaster than my smiles or touch
for brave men died and empires rose and fell
for love, girls follow boys to foreign lands
and men have followed women into hell
in plays and poems someone understands
there’s something makes us more than blood and bone
And more than biological demands
for me love’s like the wind unseen, unknown
I see the trees are bending where it’s been
I know that it leaves wreckage where it’s blown
I really don’t know what I love you means
I think it means don’t leave me here alone

I love what Neil Gaiman writes but I beg to differ with him on the last line of this poem.
If "I love you" means "don't leave me here alone" it is selfish and demanding.
To me, "I love you" means "I won't leave you here alone". Giving of oneself willingly is true love in my opinion. If you really want to be together with them you'll make the effort to stay with them and to follow them into foreign lands and even to hell as Neil puts it.