Thanks for a timely reminder of a long term concern, it's why hydrogen has to become the propellant of all aerospace. It has no pollutive output, even when combusted, actually the opposite, it cleans the air, outputting clean water and oxygen as the byproduct. My understanding is Russia has also used hydrogen previously for some experimental space flights, as well as the flights with highly toxic fuel you highlighted.
The industry knows hydrogen is coming, and expects it to happen. Rolls Royce for example have already tested some engines to work with it and all looks good.
On the materials waste deposited in the sea it isn't necessarily toxic, construction of spacecraft can be from materials created to deliberately decompose with no harmful tocixity to environment, or be inert, not decomposing at all like titanium, this remaining on the ocean bed before it might one day be recycled, would just present useful structure that sea creatures might live in. Spacecraft just need to be designed with environmental concerns in mind. I think this, like use of hydrogen will become something perfectly affordable when money changes the way it has to, to reflect the energy coming in from the sun, as you probably know I write a lot about.
The longest standing concern about space pollution, impacting still operational satellites, is the real, so far unsolvable time bomb. It stands to one day remove all the satellite services you mentioned depending on.
A former international associate from working in Satcoms, who I have much respect for, Dr TS Kelso, I think is still working in that capacity, object collision prediction and detection, voluntarily (Like me now working on the global energy problem), he does it because industry doesn't do much of it, not even NASA so much nowadays, since everything went private, for profit.
Keep up the good work Ricky, I see it all as stakeholder concerns elicitation - all things driving the solution which is coming next, fully defined from the stakeholder analysis.