Look at what they rapped about and built their careers on, you can only rap that shyt for so long before it gets stale, and/or it no longer applies. Jay found new shyt to rap about, although its debatable whether people care for his billionaire flows, nas always had quality stories to tell so he floated along effortlessly. Honestly, only dudes like ATCQ, Kast, Face, common, mos def, etc set themselves up for long careers (even though they might not be as popular, their content at 40+ yrs old doesn't make you cringe). No one wants to hear mob deep bodying nikkas 20 years later, CNN still banging the hammer, etc. it's about content and growth moreso than they can't rap any more - though some did truly just get lazy