Desktop and laptop systems tend to be in portrait orientation; phones and tablets tend to be in portrait. So you already have to either make two layout styles or accept a mediocre general solution.
Cursors and styluses are accurate, but fingers are not. So, if you make buttons sized for fingers, they feel awkwardly large (takes large hand movements to change between UI components, and the spacing means more scrolling or pages of UI), but if you size them for cursors/styluses, they are frustratingly small targets for touchscreens.
You can probably assume that most devices in portrait orientation are that way so they can be held in one hand leaving the other free to work a touchscreen, so you only need to handle three of the four combinations for a comfortable user experience in those regards.
However, there's more to it than that. Desktop users often run apps windowed, while phones tend to omit that option entirely. Mac puts the menu bar at the screen edge regardless of the window size/position, but other desktop/laptop OSs usually put the menu bar within the window border. You can remove the menu bar entirely and draw a hamburger button into your UI, but desktop users have the expectation of a menu bar and the change in convention will make the app feel like an outsider.
A desktop/laptop user will never try a long press and don't have a menu button, both of which have been used to hide extra functionality on phones, but they often do have a keyboard, and there is a massive list of keyboard shortcuts that they will automatically use. Desktop UIs have a logical tab order and that selection can be moved with the arrow keys. Cut, copy, and paste function as expected. On windows, F2 almost always means "rename selected item", F1 for help, alt-enter to toggle full screen, and so on. What about the multitude of multi-finger phone/tablet gestures? You have two very different modes on input, and users' muscle memory expects your app to fully support whichever one they are using. As an anecdote, I tried writing something in an Electron app's text box, then went for ctrl-left to jump back a word, but instead it caused a page navigation and lost the entire message I was typing. That was a frustrating "this app is an outsider on desktop" experience to me.
Your decision is effectively mediocre everywhere or customized to fit the conventions for each platform.
