He's still very questionable in his own zone and has a tendency to play like he's a winger from time to time. This doesn't really address the Leafs issues, more-so a "we're glad that you've been with us for so long" contract, but the Leafs not addressing their issues is pretty common-place nowadays.
Has he earned the contract? Sure thing.
Have the Leafs screwed themselves even more? You bet they did. There goes Muzzin and Kerfoot and whatever is left of the guys that actually seem to care.
Good luck to Toronto by working with almost nothing to secure more "depth", if you can even call it that at this point.
One does need to accept that if they were going to keep Rielly, it's not like there was a way to spend any less than $7.5m.
The question is / was, were the Leafs better off saying goodbye to Mo at 28 years old, and having a 33-year old Jake Muzzin be this team's #1 defenceman; plus a bunch of cap space?
No, signing Morgan Rielly was not going to address any "issues" with the team. Generally speaking, re-signing players don't address issues, they aim to prevent future ones.
You can question, whether with Dermott & Sandin in the picture, losing Rielly was going to be an issue that his $7.5m cap hit couldn't resolve.... but in the same breath... it can't all be quantity over quality. If the Leafs are trading Marner or Muzzin, then they'll regret not keeping Rielly.