Have you guys ever thought that maybe you just aren't able to perceive the differences in modern speech and vocab because you choose not to? Maybe viewing the past the way you are kinda leads itself to not enjoying the modern world to the extent that you possibly could. Speech evolves in ways that are often very challenging to perceive, particularly if you think of modern society as somehow dumber and less apt to convey emotions through language which mostly comes off as the opinions of someone who somehow thinks that language only works "one way" aka the way they were taught it works, and the way that they personally speak in. In the example you're using here with the rap critic, words do have meaning, and playing with that meaning or lack of meaning is just as interesting and intelligent as some rural turn of phrase, and also isn't a very new concept if you're younger than say 150.

I'd hazard a guess that - at the time in which they were commonly used - "indolent and feckless" described character traits (or habits of behaviour) whereas "lazy and unmotivated" described individual behaviours.

If I take a 2 hour lunch one day and don't make my 1pm meeting, it's lazy. If I generally only make 10% of my meetings for that reason, it's indolent.

These days "lazy" is used equally for either a single behaviour or a habitual behaviour. The meaning has to be inferred from context, which makes it less accurate than the above definitions.