why its beneficial

although you wouldve probably gotten away with being a little more subtle like 5 years ago, now most people dont really "have the time" to wait until the song starts. alot of new artists seem to ignore this part of mixing until it bites them in the ass (and most ignore mixing in general)>

genres and their respective intro duration

ps: take what i say with a grain of salt, i am still learning so feel free to critique what you think i said wrong

[RAGE BEATS] if you are doing rage beats; an intro shouldnt be longer than a bar maybe even less than a bar. [TRAP] trap beats usually tend to be easier to rap to, so making a long intro with just chords and a melody could work out as a "_ type beat" but if you want to make smt like supertrap; you should either have no intro (strait to the action) or have the song start with the intro (example : the beat's volume going up or a riser while the beat is playing). [LOFI] lofi tends to have longer more repetitive beats and for those type of beats, the start should be a catchy melody or catchy chords that melds into the part that you want to repeat, but if you want to make a less repetitive beat you could probably make it a 2 bar start with a 'fade into' chords in the first bar then a melody for the second bar (and vice versa).

i would talk about other genres but i genuinely dont have enough experience to speak about them (i barely have enough to speak about these). if you have ones for genres that i didnt include feel free to write them down in the comments and give the new artists some of your experience on the genres. as said before feel free to critique what i said as much as you want.