Is there a word for people who love everything?
Solution 1:
Omniphile: omni = every; -phile = love. Xeno- = foreign things, so xenophile means lover of foreign things, not lover of everything.
Solution 2:
Besides the already-offered neologism omniphile, consider Pollyanna:
One who is persistently cheerful and optimistic, even when given cause not to be so. [eg] You call her an optimist, but I call her an obnoxious Pollyanna.