In short, NO, Code Igniter wasn’t the wrong choice. It’s a perfectly good framework. Other commenters will use other frameworks, but for most the choice is about getting the right tool for the job in hand, leveraging past experience, and personal preference.
I’ve been using Code Igniter for a couple of years and I love it. It’s fast, capable, well documented, and it’s not over-engineered like many of it’s competitors. Frankly, after looking at other more complex frameworks (including Laravel) I still prefer CI, although I’m now using SprintPHP on top of it to give me some extra capabilities. I’m just as productive in CI as others are in their chosen framework, and I like the performance I get out of it.
As with any system, you need to choose the right set of tools, and some tools are more important than others. The language is probably less important than many other choices.
If your app works to your satisfaction then there’s no need to rewrite it. Scaling a website is a science that has little to do with the language it’s written in. It’s more about the system architecture you’ve chosen, the capabilities of the database layer (particularly in terms of replication), etc.
Don’t pay any attention to the PHP-haters. Most of them are just regurgitating the rubbish they heard from someone else years ago. Many of them have only ever worked in one language and foolishly think theirs is the “best” because they lack the ability to truly compare them, or to understand that some tools are better for certain jobs than others. All languages have their strengths and weaknesses, and those who bag languages like this are generally just exposing their own ignorance and insecurity.
There is some merit to the point that CI v3.0 will be based on PHP 5.2 and that a later version would have been preferrable. However this decision hardly deserves the vitriol I’ve seen poured on it by other commenters. CI v3.0 does introduce a large number of fixes and structural upgrades, and the PHP version will be upgraded in due time. There’s only so much a dev team can do within a short timeframe and the new owners of CI have done a great job so far. I expect to see things continue to evolve in the near future.
As long as your app works you made a perfectly valid choice. Worry about marketing and monetising your app