Novak has a couple things going for him, as far as padding his record. For one, it doesn't seem like he's fallen off from being able to channel his A game when needs to or, at the least, his B game is good enough to match the other top players on tour, except Rafa on clay.
Secondly, he doesn't have a GOAT-esque player coming up behind him. People who criticize Roger for falling off after 2009 (or 2012) ignore the fact that as he entered his 30s, he had two guys of similar talent in their primes. And as his 30s commenced, those two were always 5-6 years younger than him.
Thirdly, Rafa seems to be trending downward. Maybe he rises again for clay season, but it seems likely that he's starting to slip a bit further behind Novak. So if Rafa slips further, Novak will be the only true close-to-peak-level ATG...at least until one of the pups reaches their level.
Rafa and Novak have had to deal with each other in their primes - plus a still pretty good Roger and Andy - but part of what we're seeing as far as them still winning Slams in their mid-30s is that there aren't any true greats yet in their primes. Maybe Alcaraz and Rune and one or two others get there, but those two only turn 20 this year and are probably still a year or two away from their true primes, and several years from their absolute peaks. So Novak and Rafa have had this nice window - still lots of good to very good players, but nothing equivalent to what they were respective to Roger.
Novak (and maybe Rafa) might still have some time left as the guys to beat, but it is going to get harder and harder for them to fend off rising contenders, especially now that it seems like "Gen Millennium" (Alcaraz, Rune, Sinner, FAA, etc) might be better than Next Gen.
It isn't that different from the field when Sampras and Agassi were aging - the late 90s and early 00s saw no ATGs in their primes until Roger entered his prime in 2003 or so. Note that is also the last year that Agassi won a Slam -- turning 33 plus Roger's new level pretty much shut the door for him. Some guys like Kuerten, Hewitt and Safin were there, but we have similar players to that in Thiem a couple years ago, Medvedev, and Zverev.