Conley is a really good player, but he has never been considered a top point guard in the NBA. He's never been to an all-star game. His defense is good, but not great. Until last year, he never averaged more than 18 ppg in a year, and he reverted to below that this season. He's never averaged more than 7 assists per game.
Meanwhile, Thomas averaged almost 30 a game last year on his way to his second all-star game and an all-nba second team.
He's a good player, but is he even a top 10 point guard? Most people would take Curry, Westbrook, Irving, Lillard, Paul, Wall, and Harden (if you consider him a pg) over him. He's in the next class with Bledsoe, Walker, Holliday, and Dragic. Its debatable if he is top 10 (although I'd put him at 8 ). I'd say Thomas is in Conley's same tier.
Gasol is definitely over-the-hill. He can't play defense anymore. He has added the 3 point shot to his game which will prolong his career, but Grizzles fans know that he is not an elite player anymore. Besides, he is a 7 foot 280 bear who has had foot issues lately.
Going forward, you are probably guaranteed 5-6 more years of high level play from Love, but only 2 from Gasol (hopefully injury-free). Love can shoot outside and rebound. If you put the ball in his hands more, I still think he can be the offensive threat he was when he played with the Wolves.
Imagine what the Warriors, or any smart time, would do to Gasol with switches. If you think Love is bad on the perimeter, you should watch Gasol these days. Its brutal.