We didn't lie to you, but we weren't completely honest either. Its just a lot easier to pick one way to do things and stick to it than it is to explain all of the possible approaches with their tradeoffs.
You're starting your second job now and its going to be one of the most interesting times in your career. Its when you discover that there truly are an infinite number of ways to accomplish the same task. You'll probably find out that you have a pretty good handle on what to do, but not necessarily why you ought to do it that way.
Don't be too dogmatic. This is a tremendous opportunity to learn, both about new ways of doing things and also about the strengths and weaknesses of the approaches that you've been using. When you find yourself thinking "OMG, what the hell is this?", pause for a moment and try to figure out what the tradeoffs are: what could be some advantages to doing it this way? And ask a lot questions: "I see that you're using [tool A] instead of [tool B], why is that?" Maybe they'll have a great answer and you'll learn something new. Perhaps they'll say "We don't like it, but we didn't know a better way" and you'll have a great opportunity to teach someone else something new.
You will encounter some things that you just know in your heart of hearts to be wrong. Figure out why. You might find out that its more complicated than you realize. Even if you hold to your initial conviction, you'll need to know both sides of the argument and deeply understand the tradeoffs to convince others. This depth of knowledge, though frustrating to acquire, is what makes you better. It might not always feel like it, but you're an expert now and your new team is counting on you to help them.
Stay in touch. Everyone leaves under different circumstances. We might still be sore that you left, don't hold that against us. We've all been there before, sometimes its time to try something new. We're proud of you and wish you the best.