Slam count was never the greatest metric for me regarding which player was better. People only really started caring once Fed started to approach Sampras. Make no mistake--I'd rather my favorite player had it than didn't. But there are way too many contextual issues with slams (as well as any other singular method) to properly iron out who the best is. For me, winning 17 slams with a 90 sq racket and doing it with all out offense, while having by far the most well-rounded game the sport has ever seen puts Fed at the top (AND while doing this with such a slow homogenization of surfaces). His talent is unquantifiable and he's made the sport a joy to watch. For Nadal to pass him in my book, you're looking at something like 25+ slams (at least for me). Such are the deficiencies in Nadal's game. I say that with the utmost respect. I love him as a competitor. And certainly root for him over the failure of a man known as Djokovic.
I can't think of any real weaknesses in Fed's game at his prime. One of the greatest one handers the sport has ever seen (yes, slice counts in the convo), best forehand ever, one of the best serves ever, always been a top returner, one of the best volleyers for a player primarily playing singles (though even has the doubles olympic gold), supreme movement, one of the best overheads ever, one of the fastest movers to net ever, obviously the shotmaking, has the most matches won from two sets down (how's that for the foolish notion the man was always a frontrunner). 23 straight semi's will never be broken. The man was ethereal. His two largest rivals literally patterned their games to beat him. He was as the saying goes, the gold standard. It's taken until now with Alcaraz until we've seen anything resembling a true successor's to Fed's approach to tennis. Those are things records can't exactly quantify. Fed only has himself to blame regarding the slam deficiency now (2011, 2013, 2019 really stick out for me) but that for me isn't what's most important.
All credit to Nadal today. He's been willing to suffer the most to win as much as he has. All that said--let's hear no more of Fed having a weak era with the amount of mugs Nadal has been able to feast on for his finals. Ruud is possibly the worst slam finalist of the last 30 years, and I mean that with all seriousness. I think too many people quantify end result (winning) as the measure of who is the best. You see this in lots of sports. Unfortunately, context is rarely afforded. Most players will say Fed is the greatest they've ever played, and that's from those who have played all three at their prime levels. Zverev is the only one who seems to oscillate depending on his head space after matches. But listen to his brother Mischa. Fed puts a pressure on a player no other player can.