The thousand year peace should outweigh ten years of being fooled by an evil Sith and twenty years of nonexistence. Until Kylo Ren came along, Luke had revived the Jedi. The Jedi were not in the wrong otherwise. About attachments, none of the Jedi are immune to feelings. Not even Yoda. But he is not consumed by them and he does not act based on them primarily. After the revival of the order, Luke made an out of character mistake that cost everything. Even that shouldn’t outweigh the good that many other Jedi did including Luke.