Practically-speaking, I don't know quite what love thy neighbour means. The way I think about myself is different to the way I think about you. That isn't a bad thing. Nature makes me somewhat selfish, certainly likely to prefer my family to strangers and to wish to survive.
So it is a nice sounding thing but not reality, in my view.
If it means "try to be kind wherever possible", then that is useful. Altruism doesn't just benefit individuals. An altruistic society is also an efficient one. Or so the game theory people tell us.
But are there circumstances in which being kind is not sensible? Of course there are. I will be kind if you are not trying to kill me. But if you are trying to kill me, I will be kind to myself. In a zero sum situation, such as an insufficiency of food, sometimes being kind to you (giving you food) is going to be unkind to someone else (who goes hungry).
Life isn't so easy. It's pretty easy to say something which sounds good. Much harder to make choices in context. To rise to the level of truth, a principle must be universal.
This isn't an assault on Jesus or those who said the same things about compassion before he did. He was saying the things which made sense to him. Being kind is mostly a wise thing.
But the point is that all principles are circumstantial. They can be mostly right, but they are never universal.
The thing about loving God is obviously dependent on your belief system. Nothing much to say on that bit.