I agree. I can't tell you how many times I've heard about interesting web sites and checked them out only to find that I cannot do a single thing until I create an account. No demo, no trial, no nothing. Of course I just leave.
Well my point here kind of is: most people agree with you. But if you do the website fully without login wall , don't bother putting in an optional login. People like it better without anyway.
I kinda miss the old days of the web when downloading a demo meant only being spammed with newsletters and marketing emails. Now something as innocent as downloading a whitepaper means months of plaintive phone calls from inside sales drones pleading "this is the fourth time I've tried to reach you since you downloaded our whitepaper a month ago. I really need 15 minutes of your time...". No, you don't.
To register and try your product I need to see the demo. Period. Please, do not spam me with newsletters and marketing emails.