CoolinInTheCut
Superstar
Or when Nas put Ether on Stillmatic?
fukk outta here
You cant compare different eras like this.
An album is one of the few tools artists had to reach their fans back then. Outside of this, you had radio, performances, media / press, etc.
Today you have the internet, where you can reach your fans (and everyone else) by just posting your music online. There's no reason to put your diss on an album today unless you want your album to benefit from the attention and streams from the controversy of the diss.