You can remove the core jquery-ui.js file using this:
<remove src="Lib::jquery/jquery-ui.js" />
Unfortunately, it's not a simple a that. Because Magento is using jQuery UI modules throughout its code, it then falls back to importing individually each jquery-ui module using requireJS, like below:
define([
'jquery-ui-modules/core',
'jquery-ui-modules/accordion',
'jquery-ui-modules/autocomplete',
'jquery-ui-modules/button',
'jquery-ui-modules/datepicker',
'jquery-ui-modules/dialog',
'jquery-ui-modules/draggable',
'jquery-ui-modules/droppable',
'jquery-ui-modules/effect-blind',
'jquery-ui-modules/effect-bounce',
'jquery-ui-modules/effect-clip',
'jquery-ui-modules/effect-drop',
'jquery-ui-modules/effect-explode',
'jquery-ui-modules/effect-fade',
'jquery-ui-modules/effect-fold',
'jquery-ui-modules/effect-highlight',
'jquery-ui-modules/effect-scale',
'jquery-ui-modules/effect-pulsate',
'jquery-ui-modules/effect-shake',
'jquery-ui-modules/effect-slide',
'jquery-ui-modules/effect-transfer',
'jquery-ui-modules/effect',
'jquery-ui-modules/menu',
'jquery-ui-modules/mouse',
'jquery-ui-modules/position',
'jquery-ui-modules/progressbar',
'jquery-ui-modules/resizable',
'jquery-ui-modules/selectable',
'jquery-ui-modules/slider',
'jquery-ui-modules/sortable',
'jquery-ui-modules/spinner',
'jquery-ui-modules/tabs',
'jquery-ui-modules/timepicker',
'jquery-ui-modules/tooltip',
'jquery-ui-modules/widget'
],
If you want to remove all jQuery/jQuery UI code I'd suggest you might be better off not setting any of the Magento themes as the parent/fallback and literally starting from scratch with your custom theme. I have done this with previous projects. The result is really clean code only you write, but the amount of work building all the default front-end functionality is huge.
src = "Magento_Theme::js/jquery-ui.js"
?