Fromal was designed to be the auto-attackers Rylais, Riot should just keep it that way. The build path sucks. Thats literally the only reason you never see it built outside of ARAMs.
Autoattack slow is a lot more powerful than an equivalent spell slow on most champions because spells have higher cooldowns (not to mention that Rylai's is nerfed on AoE spells, which offsets the only real advantage of having it on spells, so we're comparing single-target slows; let's also ignore that a lot of mages have some kind of movement impairment anyway on their spells, and that most spells have to be aimed/some have more obnoxious cast times than properly-cancelled AA windups do), and is very snowbally. Not every item translates perfectly between playstyle. Like Valk said it's supposed to suck because, like early Phage in S2, there are many potential abuse cases with the item as it is, and even more if it gives offensive stats (the same way Rylai's does). Not only are you almost impossible to catch by the things that are meant to keep you in check, you can catch almost anyone you like and snowball off their corpses, which was a huge problem with Phage (cheap early buy, gave a bit of damage and all the slows).
One thing Riot are struggling with right now, as stated by them, is finding the right place for kiting, which is integral to gameplay but potentially very unhealthy.
Also another reason you don't see it built is because other defensive items, particularly ones that give resistances, are more highly favoured in this meta. I don't know how cost-effective it is right now either.
UsernameSayWha: While it is accurate that this is not a game where you are supposed to be able to 1v5, especially without incredible skill advantage, players can improve their teamwork abilities to mitigate the 1v5. Some people will always be difficult, that is true of bots and Diamond alike. The whole point is that if you are
that much better than your peers that, after enough games, your placement is somehow very inaccurate, you will be able to carry; otherwise, you almost certainly belong roughly where you are and will have to slog it out trying to improve to make the marginal gains that represent your marginal superiority over the people you play with. Remember also that skill level is something that fluctuates enough to account for some of those gains with variables such as mood, focus, stamina, physical condition, time of day, etc.
Ranked is very grindy, it's the truth. It's grindier if you aren't making the most of every game to learn. Look for your weaknesses, seek feedback, and try to patch them up.