>>12092119Grass's liability isn't just defensive. They're the most resisted type at a fantastic 7 types resisting its STAB. Luckily, half of those are relevant types found in every meta.
Ferrothorn gets by because it has everything else going for it. Power Whip is useful against Rain, something it faces often, but honestly, if it weren't for Gyro Ball's lower PP and semi-variable power, it'd be a much better STAB than Power Whip, which is used because it's 120 base power STAB move.
Venusaur uses it because it's STAB, with the other STAB being Poison, which haha, you never rely on if you can help it.
No Poison type with a secondary typing that I know of uses Poison as their main STAB.
Pokemon use their STAB. Yes, great.
Nobody uses Grass Knot, except in lower tiers, where Dragons/Steels are less common and bulky waters are more common. It's definitely lost relevancy since Gen 4.
Sunny Beam is like it always was: used in lower tiers by the bad Chlorophyll Grasses and outclassed Fire types who have nothing better to do. It can be used with Drought in OU, but it's just a major liability to use it more than once unless you can guarantee winning the weather war.
Ferrothorn [and Venusaur if you really want to argue] is the sole gift Gen 5 brought for Grass types, and it's largely used as a Steel type with Water/Elec resists.
What Grass does well, it does well. The few types it does hit for SE are relevant types. The few types it resists make for fantastic resists.
But it's so bogged down with its weaknesses and types that resist it. One this point, Grass is best: tied with Rock for most weaknesses, and Champion of the resisted types.
There are no Grass sweepers/attackers who aren't wholly carried by its secondary typing. Each and everyone has to hybridize with support, despite having some stated well to be offensive attackers, because of how trash it is offensively [it does have nice support options, though].
