I've used Link Whisper in the past and if you really don't have the time or motivation to create links for every post, I suppose that this tool is a great option.
But if you are really serious about using internal links to increase the organic engagement of your posts, I suggest that you do things manually.
You have to understand that links are part of your content.
A lot of SEOs don't understand this.
In many cases, they completely overlook this.
Put yourself in the shoes of somebody reading your content.
When a user reads your content, they're looking for information.
They're looking to walk away with some sort of experience of value.
That's why they entered the keywords you're targeting into Google in the first place.
Every little bit counts from the formatting of your content to how long your paragraphs are as well as your choices of headings.
Yes!
Even your links can move the ball forward.
That's why I suggest that you spend a few extra minutes intentionally and purposely coming up with "call-to-action" texts using your target internal keywords.
Not only does this increase the chance that people would dig deeper into your website, but it can go a long way in increasing the overall dwell time of your site.
And given the fact that Google factors in user experience, this can only help your rankings.
I know it's a pain, but it's definitely worth it.
Make a habit of it.