The biggest challenge I notice in this community is a lack of imagination. At the risk of being critical of HN royalty, Patrick just showed that it's far easier to be snarky than imaginative.
Any implementation of a blockchain where a blockchain simply replaces a database is lazy at best, and most likely completely pointless. Almost all blockchain stories that make it on HN are financial implementations that fall in to this camp, and as such they are rightly called out as being pointless. Unfortunately the comments are a pile-on of negativity, rather than a discussion of possibilities.
The interesting work is being done in areas where things that weren't possible before, are now possible. This requires imagination and resolve.
My background is in ad tech, and I've recently had conversations with companies working on solving two big problems in large media buying agencies - bot-based fraud, and auditability of programmatic trading. These problems are being solved using the bitcoin blockchain.
I'm not invested in the success of these businesses, or bitcoin/blockchain at all - but through my experience they are solving real problems (ie. ad fraud is around a ~$5-10B problem every year for the large agency groups) in ways that weren't possible before.
So to answer the question about why the community is negative towards blockchain? The HN community self selects for a group of people who solve problems in the roughly the same ways, with roughly the same tools. It's not really a conducive environment for a technology that could solve problems in a new way with new tools. It then implements a voting system that only strengthens the community homogeneity. So once a technology like a blockchain is in the out group, it's unlikely to ever be in the in group.