The question is - is not replying to emails an effective, and professional manner of communicating in the workplace?
You are addressing the wrong core problem here.
The reason it's ineffective is because you are writing emails which can be easily ignored. This answer does a wonderful job talking through some strategies to help avoid this, but generally:
- Make your email clear and concise
- Make it easy to respond to
- Make it clear what implications of responding/not responding are
In your case, it sounds like your email violated all three of these. It was suggesting a process change for your team without them being on board, required some effort/thinking to condense current project work, and was more of a "hey wouldn't this be cool!" type email.
Your primary problem this time was sending an email when you should have have first had a conversation/etc to get buy-in for the idea.
But to respond to this question again:
is not replying to emails an effective, and professional manner of communicating in the workplace?
Yes, it can be. You can even write emails in such a way to allow this. I have sent some emails to busy people along the lines of, "Let me know if this is something you'd be willing to do" and as a result a non-response is exactly the appropriate response. Note I do not do this for emails which I actually need a response to.
But ignoring poorly written/thought through emails is a way of life for some busy people. It's more effective to do this than spending all day responding to tons of email from people who can't be bothered to put forth effort to make it easy to deal with. Many get 100+ emails a day (and probably someone will comment saying they wish they only got 100). If each of those requires several minutes on average to read, process, and respond, you're looking at hours of time and this means you don't get actual work done.
For those people, ignoring non-critical "what do you think?" or otherwise not-clear/actionable emails can in fact be the only way to effectively get work done during a day. They probably correctly figure if it's important enough someone will followup again in person/IM/phone and if not? Well, it clearly wasn't worth their time to respond.
If you have time, spend it practicing writing actionable emails. This is quite difficult and unfortunately not a common skill. For the sake of everyone receiving email, please, learn this skill.