Apart from the little flame war, it seems obvious that there were a lot of reasons to ban Genesect. Mainly of it being to versatile and putting a strain on teambuilding. It is up to yourself if you think that reason is enough. Reasons to not ban it are that it is quite frail and it can sometimes prove to not be strong enough without certain boosts / locked into the wrong move.
Just wanting to point out that burn damage is no way halfed in rain.