Network neutrality is a difficult concept to apply because its core concept doesn't map well to reality.
The core concept, in my mind, is that all packets should be treated equally, and should cost the customer the same amount per byte.
The problem is that different packets take different network paths and have different costs to your provider. The bandwidth alliance partners are exchanging traffic via peering links, so there's only the fixed costs of equipment and any port charges/interconnection fees to the peering facility. Packets sent to other destinations may pass through a paid transit link and cost the provider. If your provider charges you the same amount for both types of packets, they're not being transparent about their network costs which is bad for you, and is also bad for them, because you may be able to adjust your traffic so more is settlement free and less is paid --- but you won't do that without an incentive.
Of course, if you don't like how Backblaze manages its network, there's a bunch of other network storage vendors who you could switch to (many of which are members of the Bandwidth Alliance). Or, it's not too hard to build a storage box or two and get them into a colocation somewhere.
For your residential ISP though, for most people, if you don't like the network policies, you might have another option, but they will likely have similar policies. You don't have meaningful choice in a single residence, and moving residences to get better choices isn't a meaningful option either. So, network neutrality is a policy to (attempt to) regulate residential ISP behavior, in order to provide a reasonable policy for users. It's still a problem that it doesn't match reality, and it doesn't provide user choice, but it has gotten a lot of support.
I would rather see mandatory line sharing for residential ISPs, it's a lot easier to define and with proper regulation offers a path towards consumer choice, and gives people a way to take action if their provider has poor network policies --- if your provider runs an acceptable last mile service, but provides poor interconnection to the rest of the world, you could become a line sharing partner and provide better interconnection to the world without having to build out an overlay last-mile network (which is incredibly capital intensive and difficult)