Totally agree FearlessFreddie that, obviously, assault and drug use should not be classed as "normal" or "inevitable" behaviour but op is not very specific in her opening post about what constitutes "poor behaviour" and says that only 10 per cent have "genuine" anger or severe mood swings. I would put the figure a bit higher than that but I don’t claim to have any special expertise in the area, except as a parent of teens, with many friends and family who have teens too, whose dc are going through difficult times, especially post pandemic.
I totally agree with the op that teens need parenting just as much as they did under the age of 12 but that the kind of parenting you do needs to be different, giving the teen more trust, freedom and responsibility than previously, with those three things dependent on the other.
Ideally, the main influence on a teen should first and foremost be their parents and family and extended family, and it is the quality of those relationships that, generally speaking, prevents them [at the extreme end of the spectrum] from going completely off the rails, but that is not to say also that some teens can be resistant to advice from parents, and can sometimes be too easily influenced in a negative way if they fall in with the wrong crowd. That is not to abdicate parental responsibility at all, but parents are not always in control over who their dc mix with at school or in their local area for example. Less well off families may not have the same choices that more privileged families are able to exercise in this respect [and no I don’t mean that private schools are necessarily better, sometimes they are worse, I mean that it is harder for some families to move jobs or move house say if a teen is needing to change schools or remove themselves from a particular peer group].
So while I agree that it is very important not to malign all teens and automatically assume that their behaviour will be poor, I do think you have to take in to account the circumstances and personalities of individual teens at a fast changing developmental stage where their limbic systems are not quite aligned with their frontal cortexes, which can be very challenging for them and their respective families. To say "all teens are lovely" is a bit simplistic imho because while being absolutely lovely in every way they can at the very same time, generally speaking, be quite self centred, moody, impulsive etc. That doesn’t in any way take away their essential loveliness ifyswim, it just means that they can be a bit up and down, lovely one minute and a bit challenging the next. You love them all the same, just as you would a grumpy toddler, that does not change, despite behaviour which is sometimes less than optimal! They are a work in progress, and like all of us, not perfect!