[{"wine":"Red xxx","year":2018},{"wine":"Red yyy","year":2017},{"wine":"Red zzz","year":2017},{"wine":"White 1","year":2016},{"wine":"White 2","year":2013},{"wine":"White 3","year":2017},{"wine":"White 4","year":2009}]

db.collection.aggregate({$group:{_id:null,"lastYear":{$max:"$year"},data:{$push:"$$ROOT"}}},{$unwind:"$data"},{$match:{$expr:{$gte:["$data.year",{"$subtract":["$lastYear",5]}]}}},{"$replaceWith":"$data"})