"Without using canonical tag in LCD example of 12 URL, google will treat all pages as duplicate content and will hurt their SEO." No, doesn't hurt SEO
Because they are not the same page, nor do they represent the same product.
But the content on each of those pages should be substantially different which isn't that difficult to do.
The products would have different specification, different features, different consumer reviews etc.
IF the pages are not substantially different, then there could be an issue, but that just relates to the effort in creating using unique pages.
If you created a different page for each color of a pair of shoes for example, then yes they should be combined with a canonical tag. In this case the main page would be canonical, and each color would reference it.