Hi TrafficTitan and
welcome to WebmasterWorld [webmasterworld.com]
It's really more than just using a tool to count keywords on a page.
There are 2 places in GSC where you can view the phrases & keywords that brought visitors to your site:
1.) Search Traffic > Search Analytics > Queries...
2.) Search Traffic > Links to Your Site > How your data is linked...
These are your keywords & phrases. Gathering this info over a long period of time & factoring in the variables (seasonal, economic, holidays, ad campaigns, other changes, etc) will give you a summary of what is actually working for your page.
Then, use the logic that the Google support article outlined.
Another factor to consider is the amount of content. Using "widgets" 8 times in content less than a hundred words may be pushing it, but may seem natural with 300 words of content.
Don't forget to count your Meta Page Title, Description, H tags, etc
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