It may not be as annoying as you think (or maybe it is). The app that you add for Slide Over or Split View must already be on the Dock, but unless you change the default setting, the previous three apps you've opened are already going to be on the Dock. In my experience, that's usually enough to get things done. So, let's say you've been in a Safari session and decide to work with Notes (which isn't in the Dock) with Safari in a Split View:
Click Home button to switch from Safari to Home screen > open Notes from Home screen > slide up to open Dock > Slide Safari up from the Dock > Drag down on Safari Slide Over to convert to Split View.
Since you can permanently add a fair number of apps to the Dock, you may already have the apps you need to Slide Over/Split View already on the Dock.
Further, Split Views are preserved in Multitasking. Just open either of the two apps from the Dock or Home screen, or go into Multitasking (double-click Home button) and tap on that screen's view to re-open the Split View.
And an app open in Slide Over is persistent - if you switch to another app or existing Split View, just swipe from the right edge to re-open the Slide Over app.
Now, if your aim is to have things exactly as they are in macOS... no. You have some new moves and paradigms to get used to. Once you do adjust you may find this to be far more flexible and useful than you seem to think.
For more on how to do all this:
https://support.apple.com/ht207582