I understood that BIP-110 aims to reduce node costs by limiting certain non-financial transaction patterns.
That is the alleged goal, but it is nonsense. Outlawing certain transaction patterns just means the same space is taken up by other transactions that pay lower fees.
Arguably, it is even counter to the stated goal: data storage bytes are about the cheapest in terms of actual processing impact, as they do not contain signature checks or other expensive opcodes, and do not interact with the UTXO set. Outlawing them may well end up causing them to be replaced with per-byte more impactful transactions. Or of course, those who have demand for data storage may switch to different patterns.
The bound on resource costs for node operators is the block weight limit. That limit has been the same since SegWit activated in 2017. If one believes that limit was too high, and still is too high 9 years later, the only real solution is introducing a different or lower block-wide resource limit.
There is no objective reason to outlaw these patterns; they are simply not objectively harmful to nodes. It is entirely fair to dislike them, as they are a sign of insufficient competition for block space from payments. But outlawing them for that reason is addressing the symptom, not the cause.
If affordable full nodes are essential for decentralization, why is transaction neutrality considered the more important principle?
They absolutely are, but I do not see any evidence that the current limits are insufficient for keeping full nodes affordable, and see even less reason why BIP-110 would have any positive impact on that.
With that, there seems absolutely no reason to throw out the number one value proposition Bitcoin provides over literally every other currency: censorship-resistant money. If the Bitcoin ecosystem can end up agreeing to outlaw such an arbitrary subset of disliked transactions, and even demonstrating the arbitrariness by making it temporary, I cannot see how it can realistically claim to care about censorship resistance anymore.