Use ajax to hide from search engine?

Question

Search Engine Optimization

I'm watching a webinar on SEO optimization, which talks about the problem of duplicating pages and content. Duplicate pages create additional GET parameters that need to be excluded from indexing, as the solution the author suggests using ajax, there are no parameters, there are no problems.
Talking about duplicate content, he says either not to duplicate it, or also load it using ajax.
Is it possible to just put this content in the noindex tag? Or is ajax more reliable?
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Although search engines are well aware of the content that is loaded using ajax, the author found some strange method, the webinar was held in 2015, maybe then it was relevant

Answer 1

1) Use normal CMS - they do not create duplicates at all
2) This is not an option, the search engine will index empty pages with different GET parameters, but users will see different content on them, so what, the search engine will see empty duplicates
3) About noindex - this is a solution to a problem that shouldn't even have happened, so it's pointless

Answer 2

depending on where you get duplicates grow
if there is repeating content on the pages and at the same time it should be so, then part of the content, of course, should be hidden noindex