I think it’s probably a safe bet the plugin isn’t an issue given it’s used in a lot of different sites without slow down.
Your best test-case scenario would be to load up WordPress using the same environment you have your current site on and add Elementor with only twentyseventeen and see if you’re experiencing massive slow downs.
If you are and after disabling it, it’s okay then maybe there’s a case to consider.
From themes, site caching by the host, to the other plugins you have installed it’s premature to only pin Elementor as the problem.