They do matter a lot. Blockstream still controls /r/Bitcoin and bitcointalk.org and the bitcoin repository. BTC is still the #1 by marketcap. Also, they are attacking BCH constantly.
Attacks might just be a response to /r/btc from their perspective - not everyone in BCH is a saint - Blockstream investors are mad; they literally lost millions of dollars
Also, I can't subscribe to the idea that Blockstream has investors (outside of 1-2 insignificantly small ones). These are enablers and BSCore was never intended to make money.
Forgetting about them is good. It's important to learn from past mistakes and move on - /r/btc sub looks desperate - like /r/bitcoin's jealous ex-girlfriend - I prefer /r/bitcoincash