Consider the two ways you can be wrong here: you can omit it when the right thing is to include it, or include it when the right thing is to omit it. One is much worse than the other.
If you include it when you should omit it, you believe (without evidence, you’ve just heard horror stories) that it might delay your application. (“I will have to provide explanation for name change, reason for name change and they could ask additional documents too. I’ve also heard from people that they keep applications on hold for months because of this as well.” and “they put your application on hold and do very lengthy background checks and ask dozens of documents on previous name, and all this for nothing”) This sounds bad. But it’s just rumours. There isn’t a spot on the form for “Why did you change it”, and you don’t have information on the web site that including this information will actually slow your application, nor what the “dozens” of documents are that you supposedly would be asked for. (I have not applied for a Canadian visa, because I’m Canadian, but I have applied for other visas, and included my former name (I changed my name when I married) and no country ever came back and asked for more details about when and why I changed my name. Just one data point, but possibly useful.)
If you omit it when you should include it and this is discovered, your application could be denied rather than delayed. Not only will you not be admitted to this country this time, for the rest of your life you will have to answer “yes” when asked if you’ve ever been denied entry to a country. (This tends to get you denied entry to whoever was asking. It certainly delays your applications.) Or if you get admitted this time, if the omission is discovered, you could be expelled or deported, with again permanent consequences for all the countries in the world you might want to visit.
Your question boils down to “should I lie on my form to speed up my application?” and I think you know the answer to that is No. Not just because lying is wrong, not just because you don’t actually know that it will speed things up to omit your previous name, but because the consequences of being caught in this lie of omission will be enormous and you won’t be able to fix them. You will just be someone who can’t visit other countries. Don’t risk that.
You may think you can get away with it because you didn’t use the old name on visas etc, but you changed your name legally in your country and it’s probably pretty trivial for the government to check if your current name and birth date are associated with a name change. The reason they ask about old names is because they may do a search on you, and they want to search using all your names. If they do a search and find your old name, you will (at best) trigger all the extra paperwork you wanted to avoid, or just be denied irreversibly for lying.