Pure Deathwing has been “dead” since something mid-Fifth Edition to Sixth. GW
made the decision long ago that “competitive” play wasn’t going to see spam armies like Deathwing where the army is basically all one Elite type back around Sixth. It’s not like this is unusual or hasn’t been telegraphed by the way they’ve written the rules and Codexes for Dark Angels for the last eight years - whining about it now is a bit of having missed the boat. Expecting them to change that is at best a false hope.
I have probably 50-60 Terminators that I could use to play, and I will - in a reasonable narrative game where the army makes sense. However, full Deathwing armies are not the normal mode of operation for the Dark Angels, so seeing them on the board that way should be the exception, rather than the rule.
As far as the local community - be a trend setter - challenge people to non-tournament style games, talk with folks, get them to see that it isn’t the only way to play. Set up with your local shop a non-tourney night where people can play Kill Team, Necromunda, narrative/open play games, etc. If your players locally are so absolutely stuck in the tourney mentality that they really can’t comprehend or accept playing a different way, I’m really sorry for you - that absolutely sucks, because it isn’t the only way to play the game and people should agree to have fun first.
So let’s be reasonable regarding the beta Deepstrike rule: if you really want GW
to listen, don’t rant and rave and complain how they ruined your army - that may have actually been their intent. Instead, show how you could have fun with your army and purchases you were intending to make before the beta rule was written, and be realistic about it, they will probably smell bullcrap if you say that you have 80 Terminators and we’re planning to buy another 80 in plastic with the new kit. Then contrast it to how games are played now, how it fundamentally changes how the army works, etc. Whatever you do, don’t mention “Now I have to buy things I never wanted to!” That indicates that you might buy stuff to keep playing, in other words you’ll keep being a customer. Indicate that you are willing to keep being a customer, but things have to change back so you can continue to have fun.
Beta rules are a test period - they’ll listen to feedback about it better if you actually show you tested it, rather than just complaining without having actual game descriptions in there.
In the end, playing in a competitive situation is about adapting and overcoming - view this as the challenge and adapt and overcome and show everyone that you are a true competitor.