Simple - I do not know you to trust you. You might be a perfectly reasonable guy. I don’t think we have chatted before to know. That is all. Genuinely it. My aversion to starting an argument on a log is close to 100%.
This is wrong. I trained on unsprung floors for years. And whilst I sustained an injury, this was because I decided to fight a super heavy weight European champion competitor. Week to week - training was not painful at all. It should not be. If it was - then you were taught wrong. As evidence - we had an 82 year old man train with us. Full throws as well. 82 year old me can not train through pain.
This a teaching issue. Sorry but it is. Progression is for the most part not “that hard” I saw guys with 0 experience become competitive in local competitions within 9 months.
With regards to your shoulder throw - not everyone is good at every throw. I trained with guys that had competed at international level who were worse at some throws than me. A yellow belt. Having a crap throw is fine / normal. Mine was hip throw. The 1st throw.
So the idea that Judo is bad as a hobby as its painful and hard is wrong. To be fair weight lifting has caused me more pain, and is harder. But this is also a point. Things that are hard and painful make great hobbies. As the point of a hobby can be to test yourself. To be the best you can. And any one can be good at soft and easy.