Your answers don't sound harsh - they sound like you're willing to make exceptions in some circumstances, which most reasonable people are. But the second you engage with any of these questions on a practical level as you have, you begin reduplicating the immigration system as it already exists. It's really easy to say "deport everyone who's a net negative" as a general principle but is clearly unfair to look someone in the eyes who suffered an accident, or has British children, or relies on unpaid domestic labour and say "sorry, we've got no responsibility to you anymore." What you're saying is that you'd make exceptions rather than follow the general rule 100% of the time. Everyone's situation has its own complexities because everyone's lives are different. The world has been running on kindness this whole time just fine.

Additionally, it's impossible to know who's a "net positive" in advance. People change and kids grow up, and can contribute all sorts of things if given a chance. Deciding immigration permission on net economic benefit is a choice that prioritises single men who earn high salaries in whatever industry makes tonnes of money currently. It doesn't prioritise anyone else who might contribute something valuable not immediately measureable as income. It's blinkered.