Disclaimer: I’m currently a free user and have no plans to upgrade.
I think you can stop the notifications and emails using one of the privacy settings in the app. Personally, I’m not particularly bothered by the blue upgrade card, but I can definitely see how it might be annoying for some
I agree that Monzo need to focus on improving the basics (payments, user experience, basic budgeting, customer support) as well as improving their paid offerings and business banking.
And to be fair to Monzo, they do seem to be doing just that - there’s now a Core App team that focuses solely on improving the basics and that team is currently doing excellent work on the Payments tab. I also think the app’s general UX and speed has improved over the last 6 months or so, along with customer support.
I think stuff like advanced budgeting features makes loads of sense in paid tiers.