Are all these main services really "rivals" though?
Disney+ will (eventually if not already) be the only place to get Disney content (inc. Marvel and Star Wars). Netflix and Amazon have different stuff still.
So:
if I want Amazon Originals I need to pay for that
if I want Netflix Originals I need to pay for that
if I want Disney/Marvel I need to pay for that
if I want Apple Originals I need to pay that
That isn't "rivalry" to me - not many people will only have 1 and if they do it will be Netflix for the greater selection. No one is going to bin Amazon and/or Netflix and replace solely with Disney+. Rivalry is all having the same content and you then get to choose the best price/experience. Basically like a car: Vauxhall, Nissan, BMW, Mercedes etc. are rivals in that you only need one of their cars for the entire act of driving. HP, Dell, Acer, Lenovo are rivals in the same way.
Then you have BBC iPlayer, All 4, My5 etc. and I can see before long basically every traditional distinct TV channel will move to their own distinct subscription service. So we'll have 2 dozen services, 2 dozen subscriptions, 2 dozen disparate interfaces within those services' apps and so on.
What TiVO, Sky, Virgin etc. have all done in content aggregation in a single, consistent UI will be gone.