"Google+ is not longer available for consumer (personal) and brand accounts."
This is what you'll see if you log into your Google+ account as a user or brand that does not have G Suite on or after April 2, 2019. What does that mean for your marketing and website? Not too much!
Search Engine Optimization (SEO)
Unless you were entrenched in using Google+, you won't see any impact to your SERP rankings.
If you were extremely active, the impact could be little, if at all. Several years ago, Google did use Google+ to influence the personalization of results for local search. Google's testing revealed that it didn't help users find what they're looking for and didn't help improve search results. In addition, Google+ had previously been removed from Google Local and Google My Business.
However, if your company's listing on Google My Business is not claimed or verified, stop reading right now, claim your listing, and fill it out. This is extremely crucial in any local SEO strategy. Here are some helpful hints from Google on how to perfect your profile.
Remove all Google+ icons and links from your website, even if you do use G Suite (here's more information for G Suite subscribers).
If you do have a link on your website to Google+, it is a dead link (and results in a 404 error). There's no need to delete your account, as Google will do so in the coming months. Simply removing the links will suffice. (Don't forget to remove Google+ from any collateral you might have too!)
It's likely that Google+ wasn't a large part of your social media strategy. This is a good reminder to evaluate your strategy, and focus on other networks that might be better avenues to reach and communicate with your audiences.