I don't think some bad lottery luck would hurt too badly for the Celtics. I think the team is in a strong position regardless of whether they come out of this draft with a top five pick. I am more focused on how well they are positioned to make a big trade or FA acquisition over the next 18 months or so than I am on this year's draft.
If they get a top 3-4 pick, great. If not, it's not the end of the world. They'll still have a good pick (5-8) and a chance to do something with it.
I don't think Boston is as reliant on hitting a home run in this year's draft as any of the other teams down in the lottery ... because they have more talent on their books than the others, have very good cap flexibility, and lots of trade assets and future picks. Regardless of how this year's draft plays out, I think they are well-positioned to succeed in the medium to long term. That is something that very few (any?) other teams in the lottery can say.
Obviously it would be much better if they do get a top pick but I don't think it hurts Boston as much as other lottery teams if they miss out.