Well that's wrong on multiple counts.
First:
which is why there are so many errors in permabanning
The failure rate of the IFS is minuscule. And that includes more then just unjust permabans, but for any kind of punishment it doles out,
Second:
groups of premade people can get someone banned near instantly, but people who solo never can get the premades banned
That's not how the system works at all. All it does is check if there were reports in the game, and then analyze the chat log for the reported player. Multiple reports in the same game have no more weight than one, and it is specifically set up that way to ensure that premades can't get a solo player punished for nothing. The only way you will get punished is if you are actually toxic.