Google Adsense is a good way to make money online. It won't necessarily make you rich but you can earn a little extra here and there. If you end up duplicating a successful campaign you might make some good money, but a lot or website owners think that just by putting a little bit of Google Adsense code on their webpages they will walk away wealthy. Please be aware that it takes more than just that.
There is no doubt that Google Adsense is a good program on the internet to earn an income from your website but there is more to the equation. It takes more than just adding the code to the webpages and quite often it is the more experienced internet marketeers that start making the good money through Google Adsense. You need to accept that Adsense can't work on its own. You have to do the patient and experimental work.
One of the big reasons is that you are relying on visitors clicking ads that other webmasters have written to promote their site. If the ad is badly written then the visitor might not even notice it. You also don't really have control which ads appear on your webpages. Visitor's have become harder to persuade as many may have been misled and scammed before.
A lot of webmasters using ads might give false hopes and the website might lead to an adware site and if you're advertising your site could get a bad reputation regardless.
Many decent abiding webmasters nowadays try and blend Adsense ads with page content to read naturally which aims to give the impression that the links are part of your site and its content, almost like a camouflage concept. It might work for you but you need to accept that Adsense is another form of income potential and not the only one.