I adopted a dog in college in an attempt to salvage a failing relationship with my girlfriend at the time. The addition of the dog briefly worked but in the end it was a really stupid idea. We ended up luckily finding a good home for her but I think that I am not alone in this mistake. I totally agree with you about people not realizing that having a dog is a lot of work. Even though my dog is extremely well behaved she puts massive restrictions on my life as far as what I can do / where I can go.
It's a big commitment and from what I have heard in the USA, there are some shelters that will not let you adopt a dog without doing some sort of background check on you first. I have no idea what that entails but yeah, people need to resist the urge to help if they aren't ready for it. Dogs live up to 20 years and will need your care for all of that time.
This happens very frequently and a lot of the dogs that have ended up in our care are a direct result of this sort of mistake. I'm happy that you learned your lesson early in life. Now if we could just get everyone else to understand this as well