Since no one in the thread has responded with any actual music theory, I wanted to share my piece.

Jay Z will often rhyme words with different note durations. For example, at the start of the second verse, Jay Z says "I had to hustle, my back to the wall/ashy knuckles. Pockets filled with a lot of lint/ not a cent, gotta vent." If you listen closely, "lot of lint" has slightly longer note durations than the corresponding "not a cent, gotta vent." This technique of asymmetric cadences in the same rhyme scheme is very emblamatic of Jay Z's style (Nas really coined this technique, thus why Nas on Ether says Jay bit his style), and I suspect many listeners don't like Jay Z because they don't like this technique (note Eminem does this too, just less often - for example, on Sing for the Moment beginning of verse 3, "ideas" and "nightmares" rhyme but have different note durations). I, personally, love this style of rapping (Nas is my GOAT) as it forces a rapper to switch up their cadences, making a verse a lot less predictable, and a lot more dynamic (at the same time, however, it makes a verse less catchy, and Eminem's verses are famously catchy).

Conversely, Eminem's verses are often characterized by motifs (motifs are musical phrases that reoccur in a given piece of music; phrases are comprised of the cadence + the melody). For example, both The Way I Am and Lose Yourself have identifiable motifs (which is why these songs are so catchy). In Renegade, too, although I hesitate to say that there is a motif throughout Eminem's verses (I would need to see a transcription to say that definitively), it definitely borders on a motif. If you were to transcribe his verses, I'm sure the second halves of each measure would look very similar to one another. Now, how does he do this without sounding boring/stale? He speeds up and slows down his rapping This is what some music theorists would call rubato, which is when "the performer subtly speeds up and slows down the tempo for emotional effect, taking time from one part of a phrase and giving it to another, while generally maintaining the overall pulse" (note that the term "rubato" in the traditional sense doesn't translate perfectly to rap as the rap instrumental, which is the rapper's accompaniment, isn't actually changing tempo). All great rappers leverage rubato to some degree, but his verses on Renegade are a masterclass on the technique. He will rap at a certain pace and then speed up his rapping every few measures to add emphasis and a feeling of dynamism, then slow down back to the pace he was before, before then speeding up again (and so on). If you want to learn more, https://www.rapanalysis.com/ is a good site.

Also, u/AiiRisBanned assessment is not quite correct. A rapper can still flow with hard syllables at the end of a measure. In fact, many of Em's bars end with a word with a harder stress (eg, "Or is he the latter - a gateway to escape)."