I developed my first Ionic project for an university. I had small issues about lazy loading like routing animations. It’s not so important but i think about title question. Is lazy loading really necessary? Especially for a small project. For example we have 5 public pages, others are for students. If i convert 5 simple pages to eager, does it really effect performance? Or lazy loading is default for large projects like 100 pages?
Thanks in advance.
Try googling ‘angular lazy loading best practices’.
The idea behind lazy loading is that we only download the HTML, CSS, and JavaScript that our application needs to render its first route, and then load additional pieces of our application as needed. The great news is that a new Ionic Angular 4.0 app has lazy loading configured by default.
see this : How to Lazy Load in Ionic
I know it from Angular. In Angular world it’s not used for -just- first route. It’s used for rarely used pages like register or login.
In mobile, chunks does not come from server. So angular & ionic lazy loading logic is some different, i can understand it. But still chunks needs to be downloaded.
I asked this because i had an issue. Ionic menu (in fact routing) has animations. When i click a lazy loading page, animation has a -short- delay but it’s noticable. I’m sure it’s because of lazy loading. Second visit works well. 
So, on a 5 page app, with a low amount of resources, a more accurate question is “Will using lazy-loaded modules/routing help improve experience?”. In your case, probably not. 5 pages is not really even an ap. It’s a toy. However, a real enterprise app, with “100 pages” as you say, YES, lazy-loading would probably prove to be a game-changer in performance, especially if you are using things like forms, a lot of styles, lots of different libraries across various pages.