Is a 4.2 second mobile load time killing my conversions?

My store loads in 4.2 seconds on mobile according to Google PageSpeed Insights. Desktop is fine at like 1.8 seconds but mobile feels sluggish when I test it on my phone.

I'm running about 8 apps (reviews, email popup, loyalty program, the usual stuff). My product pages have 5-6 images each. Nothing crazy.

Conversion rate has been stuck at 1.8% for months and I keep wondering if it's the speed. But I also don't know if 4.2 seconds is actually bad or if I'm overthinking this.

What are your mobile load times? And has anyone actually seen conversions improve after fixing speed issues?