I just wanted to add one thing...
I actually think you have done the RIGHT thing by sticking to a set of "rules" and whoever drilled that into your head probably had the best intentions
The reason I say that is when you are starting out in songwriting I personally think your songs will sound "better" (ie more professional and like what is played on the radio so people listening are more likely to subconsciously recognise the similarities between your songs and the ones on the radio therefore your songs must be "good")
You will have also learnt a little about the "discipline" of song/lyric writing by sticking to a rigid structure - even if you come up with completely different rhyming schemes, there will always come a time when you are sweating over that killer rhyme or word in a non-rhyming situation
I would therefore challenge you and say you haven't been "brainwashed" or that you have wasted your time - I would put a much more positive spin on it and say that you have learnt one approach to writing songs and now you are hungry to learn different ways - and you have come to the right place so welcome to the forum, there are plenty of people here that will help, guide and answer any questions
I personally feel that the arrangement, structure, rhyme scheme etc. should be dictated by the "concept" of the song and the message you are trying to communicate
A sad song may not have many rhymes, have lots of drawn out syllables and "held notes", with an "awkward" rhyme scheme to add some tension - eg the "cloud" in STC's excellent example
However,
If you are writing a really upbeat song then you may want to consider lots of rhymes, including internal rhymes; lots of syllables to keep the melody "bouncy"; a straight forward and predictable rhyme scheme so the listener can relax and be satisfied when the rhymes come in all the right places
It is true that there are no rules and the Songwriting Police are not going to come knocking at your door
BUT
There are proven "tips, tricks and tools" (which I still call "rules") that CAN be followed to help make you songs sound "better" to "joe public" (see definition above)
My view is that you SHOULD learn the rules by watching videos, reading articles and books - knowing the rules doesn't mean you have to follow them all the time and when you break them you can do it in a considered way to add IMPACT to your songs
Just my quick $0.02