Everyone's definition of 'complicated UI' is different, as is the amount of reactivity you have in your app (e.g. when this data changes, what else in the UI needs to change?).
There is one caution I will give: try and predict where you will be in 2-5 years. 5 years ago I built an app with complicated screens server-rendered with a smattering of Vue to enhance them. We are now moving more and more of the screen into Vue because the reactivity has increased. It would've been better to decide to build _this section of the app_ in Vue from the start, though situational constraints (aka the budget) would have prevented us from doing so anyhow.
Everyone's definition of 'complicated UI' is different, as is the amount of reactivity you have in your app (e.g. when this data changes, what else in the UI needs to change?).
There is one caution I will give: try and predict where you will be in 2-5 years. 5 years ago I built an app with complicated screens server-rendered with a smattering of Vue to enhance them. We are now moving more and more of the screen into Vue because the reactivity has increased. It would've been better to decide to build _this section of the app_ in Vue from the start, though situational constraints (aka the budget) would have prevented us from doing so anyhow.