If Steam had not come along another digital distribution system would have, there's a high chance of that. You give Valve way too much credit they do not deserve.
Would there have been other digital distribution platforms? Most likely. Would they have been even remotely as successful (and thus influential) as Steam? I seriously doubt it. When Steam was first released, everybody hated it, even though it came from a company with one of the strongest reputations amongst PC gamers. However, Valve worked hard to improve Steam and it slowly earned the favor of the community. Now, it is by far the most successful digital distribution platform and is largely synonymous with PC gaming. I think any credit given to it is well-deserved.
Your entire argument seems to rest on an irrational disdain for Valve. The facts don't support your position yet you persist regardless. If you can provide a cogent argument supported by objective facts, you'll be more likely to convince others. Unfortunately, the facts all prove that Steam has been beneficial to PC gaming so you'll have a difficult time convincing anyone otherwise.