The closest I could get was xenophile. Also, optimistic would be a close second and I say that because I don't think that optimistic is a better description than xenophile because xenophile actually includes love.
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Omniphile: omni = every; -phile = love. Xeno- = foreign things, so xenophile means lover of foreign things, not lover of everything.
Besides the already-offered neologism omniphile, consider Pollyanna: