I think he's done okay, so far, considering. Something to keep in mind is, he's a very different player from JR, so the team needs to be able to play to a different set of strengths. Jack and Tom are both very good kicks - Tom might be a tad longer I think. They can both take a mark, but Jack has more of a leap and more of an ability to twist and manoeuvre his way into one, out of relative nowhere.
I have always rated Jack very highly, so much so I'd put him before his cousin, notwithstanding all the accolades. Simply because he's a better kick than Nick was, more reliable, so the momentum loss at a key moment doesn't occur as often - Nick was better around the ground, admittedly. These are just examples, but remember that in BOTH the 2017 GF, AND last year's horrific PF effort, Jack was outstanding - about the only one you can say that about.
Anyway my point is, I've seen enough so far, to consider Lynch worth the bucks. If we could ever get those two running as they could be together, it'd be pretty devastating I'd think. And yea, Lynch needs some more time, and the team needs more time with him.