I do use a physical keyboard with my iPad. I'm a touch typist, so physical feedback of finger positions is vital. I started using PCs before Mac/Windows came along, so I've been using keyboard shortcuts for a very long time. They can be very efficient, because both hands remain on the keyboard. In most cases, it makes little difference whether I remove a hand from the keyboard to grasp a mouse or to touch the screen - my writing comes to a standstill while one hand is occupied elsewhere. However, keyboard shortcuts are not universally more efficient, so mouse/touch will inevitably interrupt my writing from time to time.
In terms of efficiency, I prefer to highlight text with my mouse (right hand) while executing cut/copy/paste/bold/italic, etc. with left-hand keyboard shortcuts to any kind of mouse/touch-based invocation of those commands. And when I'm doing something other than writing, my computing world becomes mouse-/touch-centric..
As keyboard-centric as I am, I find it far more efficient and precise (on Mac/Windows) to use a mouse or trackpad for highlighting text than to use the keyboard. With decades of mouse experience behind me, I have wished for a mouse when keyboarding on my iPad - it's my natural go-to, and the touch interface method for selecting text seems clunky in comparison - it's harder to place the insertion point exactly where intended, and dragging two grab handles (to make up for that initial imprecision) rather than a single click/drag of the mouse.... In that regard, I'm looking forward to trying out the new approach announced for iPadOS.
Still, as I see it, the "I want a mouse" contingent is asking for a minimum of adaptation when moving from PC to iPad. That's not necessarily a bad thing, but since iPad was designed from the ground up for touchscreen (just as macOS and Windows were designed from the ground up for keyboard-plus-mouse), learning and using the native interface will tend to deliver the best experience - practice makes perfect.
Ultimately, I'm on the side of "get over it." Learn to use a touchscreen like a power user, rather than wish an iPad was exactly like a Mac.