4 seconds on 4g isn't too bad. Less than 3 seconds is achievable, 2 main factors:
1) How optimized is your Shopify theme.
2) The load time of your store facing 3rd party apps.
My team has optimized hundreds of Shopify sites, collected and organized data into benchmarks: https://speedboostr.com/shopify-performance-benchmarks. That can give you some insight where you stand and where you can go.
For the factors above, you can check / solve #1 with the Shopify Analyzer - a free tool we built for the Shopify community. For #2, this is a preference and a balance. Each store facing 3rd party app will usually add to load speed. You can mitigate that by hard coding app features directly into your theme (if applicable).
I don't recommend uninstalling apps just to gain speed - if they're producing revenue and engagement they're helping your business... so my recommendation is focusing on theme optimization first.