People will forgive a lot, but slow sites speed tends not to be overlooked by humans or search engine crawlers. It doesn’t matter if most of your traffic is from desktop browsers; in September 2020, Google switched fully to mobile-first indexing. It’s worth noting every update Google (no matter how much AI is used) has rolled out in the past five years seems to place a greater priority on mobile site performance.
All those cool widgets and embeds you like because they make your site “better”. You know the chatbox, Yelp reviews carousel, the fly-in Instagram imbed that looks like a 90s PowerPoint slide, that neat jQuery-driven social share widget &c, those are making your site slow, and that’s bad for both UX and SEO.
In rare cases, that one widget will increase the conversion rate enough to be worth the trade-off in speed. But, at an added .5-2 seconds of mobile load time a pop, how many of them do you really need? As a general rule, you cannot do things that make your site notably slower negatively impacting your site’s ranking in Google search and increase your overall conversions, even if you somehow increase your conversion rate.