Why do I feel you are deliberately choosing not to see the other POV? Let's forget for a minute that you seem to have the ability to tell apart a user transaction from a spam transaction and suggest that actually the daily demand for transactions rises above 250,000 consistently. Tell me how exactly users who are unable to get a transaction confirmed (they just sit there ad infinitum) are not 'disrupted'?
Since when did failure of transactions to be written to the chain become a feature? It is a sign of failure.
You said:
The best bit is that as the network becomes increasingly congested actually performing a flooding attack to completely disrupt the network becomes trivially cheap to employ.
And I just noted that the network cannot be disrupted (let alone "completely"), it will continue to process its 250k txs per day, with the highest-paid-tx-gets-included queue.
The idea that every tx has to be included and the network must upgrade to compensate is wrong because it is a self-feeding loop that tends to infinite spam and abuse. If I am a spammer and you give me 1mb to fill, and I fill it, and you give me 10mb and I do the same, will you keep giving me 100mb, 1gb, 10gb blocks etc etc, where I fill them all? Do you think this kind of self-defeating system is some kind of "success"? Are there many blockchains, beyond bitcoin, where you can do just that and where the devs haven't taken action to save their blockchain - typically through sharper fees to act as a deterrent to the attackers?
The case of having 250.000 legit txs and zero spam, and them having to compete for that 250k tx space is just theoretical. Why? Because actual txs are way below that point and by the time actual txs double or triple (which could take >1 year), we'll be 1.7 or even more (which is right ahead). So rejoice, more spam will be able to be included to the blockchain compared to our 700-800kb per block right now.