I think the key takeaway here is that people are allergic to that word.
Not really, it just implies that the competition is not modern, without qualification. I think asking for qualification in this case is fair if we are to conclude Redis and Memcache have aged to the point of needing a replacement.
Modern is used here as a selling point
The word is often tagged on anything new somebody tries to sell. Better to be specific. The problem is that most “modern” things are very old things sold as new ideas. Cause biz. So, nothing specific against this proj.