Advice on new UX

We have 6 large monolith backoffice desktop web applications that are almost CRUD oriented. The users of those application were complaining that in order to accomplish a business process they have to go in multiple screens in the same application and sometime finish a part in another application.

Based on that we have decided to review our approach and create a shell application aimed to host mini applications. Because all of our old big applications are split in mini applications we have get rid of our old large menu in order to switch to a hamburger menu with only two levels max.

We have also taken a multi-screen orientation (the appearance of the web application is reviewed in order to be displayed on a tablet). The application shell has a button on the left to let the user switch from an application to another using SSO authentication.

Our developers are now complaining that the old interface was more intuitive and this is why I am asking for advice on it: for example they could not find a direct menu to add a new entity in the hamburger menu and they have to load first the search screen and select action button then "new"... Before we were used to have a master detail approach : first find an item in a list and then edit it in a huge detailed screen like this :

the old search screen

the old detail screen

Now we have this new search screen :

I think that we should put the hamburger menu on the left and the application switcher on the right : because it feels more intuitive for me. But I need advice on that.

And the detail screen is modified so that we could display it on a smaller screen (the tabstrip have been replaced by accordion) :

Is the old approach was more convenient for CRUD applications ? Does the new approach have some design issues ?