Are the apps that are not present in AMP responsible for slowing my store

AMP is a standard that is quite opinionated on how web pages should be built. These mean that you have to work within the restrictions of AMP and recreate from scratch most front end functionality.  In exchange for the adhering to the AMP framework, you get speed. 

How are AMP pages so much faster?

1.  AMP pages design eliminates or restrict the most common sources of delay and tells the browser how to optimize the view. 
2. AMP page content is pre-rendered and pre-cached on Google.  As an example of what this means, consider search. When a user searches on Google , Google serves up the results in an instant and then automatically begins downloading AMP content in the time that a user reads through the results and even before he clicks. As a result when a user clicks on AMP pages, they are much faster as critical assets have been downloaded.   
3. Google gives you access to its cache servers and stores AMP content where your users are. Content is delivered from servers close to your users minimizing latency. 

Now to your question about whether functionality that is missing on the AMP pages responsible for the slow speed. The reason why the functionality / apps are not present is that the default AMP theme that you are using does not support that functionality as it has to be custom created. We do offer the main functions most users ask for and for large customers custom build the functionality in AMP. We are working on launching more sections / functionality that is supported in Dawn and Theme 2.0 themes. This is a couple of weeks from launching. 

It is true that some apps / theme functionality adds significant delay but not all. It is also possible to code apps efficiently so that one app offering a particular functionality does not give you a speed penalty and other apps that do the same thing may slow you down a lot.