Points are what matters to call a player great offensively. A guy with a career high of 34 points is not great offensively. It's like having a player with great underlying numbers but hasn't put up the points yet to match it, he's got to actually put up the numbers.
Lindholm is better than Rielly defensively, however Rielly is much better offensively. Rielly put up 36 points on the Leafs tank roster that had Kadri as the leading scorer with 45 points. That's very impressive considering how little he had to work with. Those 36 points are also 2 more than Lindholm's highest season total ever. Lindholm has the edge on Rielly defensively, but the gap is massive offensively, especially going forward.
Rielly plays with Hainsey who's a bottom pairing d-man at this point, Manson is Lindholm's partner...Manson got norris votes last year for comparison to Hainsey. Better defensively also has to do a lot with who you're playing with and the team defense as well.
Points, especially secondary and PP points are the most overrated way to evaluate players. Offense should be rated based on a players ability to create it, which puts Rielly in one of the top tiers in the league (basically with a guy like Josi) and that's not including points, which are honestly more luck than anything.
Defensively you say Lindholm is better. Lindholm is a god. He's the best defensive defenseman in hockey, and he creates chances/shots at an above average rate as well. He's much closer to Mo offensively than Mo is to him defensively, which is clearly Mo's biggest weakness looking at stats alone.
Hainsey has actually been good this season, and although it's obvious his offense is being carried by #44, Hainsey is clearly taking on the brunt of the defensive responsibilities and doing much better than people are giving him credit for.
Lindholm's partner is actually Montour this season, but Manson has been his primary partner the last few years. Much better player than Hainsey, but it doesn't limit the fact that Lindholm is a god.
I'm not even trying to chirp Rielly here, I think he's a top-15 defenseman in hockey. Lindholm is just arguably top-5 based on his overall impact to his team.