thats true, however in that 12 years I have talked to thousands of people with their first gsd, and the most difficutly any of them have mentioned is that the dog is challenging, in that they are ABLE to constantly teach it new things. not that they have to teach it new things or constantly train it, but because the breed has the ability and desire to learn new things.
you may have done great with your gsd and therefore be able to raise another breed just fine, but that has nothing to do with your question. you asked if there was a guard dog breed that is not as domineering as the gsd. the gsd is by far the least domineering of the gaurdian breeds, so if you found the gsd difficult then as a professional I HAVE to suggest that you avoid a more dominant breed. if you are willing to do a lot of research and train with a professional then Im sure you could do great with a more dominant breed. but if you are looking for a less dominant breed then you are not looking for a gaurdian breed.
"What other kind of training is there, besides for dog-sports which I will not do." first off why not? the gsd excells at schutzhund, obedience competitions, ring sports, flyball, agility, herding, tracking, therapy and more. besides competition...my 18 1/2 month old male is trained to sit, lie down, come, heel, shake hands, roll over, sit up/beg, stand on hind legs, bow, go get the phone when it rings and bring it to me, to sit in the middle of the room when the door is being opened or the door bell rings. and he knows his obedience commands in english, german, spanish, and we are working on french. as for other training we do schutzhund, agility, flybal, therapy work, and some herding.
no offense but you are not being clear at all in what you want. you say the gsd is domineering and you want a dog that is less so. I explain that the gsd is the least domineering/easiest to train of the gaurd dog breeds and you say that you did fine with a gsd so you should be fine with another breed. that doesnt make since. most people, if they came to me and proved they had done fine with another breed and wanted to try a more challenging breed, Id say go for it and Id help them choose a breed. but you are riding both sides, saying you want a less dominant breed, then saying you did fine so you should be okay with a more dominant breed? you very well may be fine with a more difficult breed, but the fact that originally you were asking for a less dominant breed makes me suggest a less dominant breed. if you are looking for an easier dog than a gsd (wether you did great with one or not) then you dont need to go with a more difficult breed. perhaps a watchdog, one that barks when someone approaches but is excited about it and wouldnt bite, is more up your ally. or another gsd.