Now there's nothing wrong with that, but someone still has to work for the UBI to work.
As always the first question is: Why do you mean by UBI? It seems that everyone has their own idea.
If that means a benefit to ensure everyone has a minimum income to buy basic things then this is nothing new and exists in most Western European countries. In that case 'UBI' is just a new term for an old thing used purely within the US political debate (perhaps to avoid stating that this is what those 'socialist' Europeans have, I don't know).
On the other hand if UBI means what it is supposed to mean, i.e. "is a theoretical governmental public program for a periodic payment delivered to all citizens of a given population without a means test or work requirement" [1] then you can immediately see that the main issue is indeed feasibility and sustainability because unconditionally giving a meaningful amount of money to every person in a country is extremely expensive and the money still has to come from somewhere.
There isn't any negative emotion associated with free stuff. Free stuff is great.
The issue is that there is pretty solid social ... I don't want to say understanding, perhaps suspicion is the right word ... that giving out free stuff hasn't ever worked well.
So the political faction that likes the idea of free stuff comes up with a reason that this scheme will work - trying very hard to come up with a framework where people get to consume stuff without necessarily having to do the work to produce an equivalent amount of stuff.
Much like a perpetual motion scheme, the system gets more complicated to the point where eventually nobody can explain why this specific system can't work ... but there is a core relationship here that needs to be broken, and the debate needs to centre around whether it has been broken this time. It cannot be hand-waved away. The enormous costs associated with a UBI are an important factor and there are questions about whether it can be sustained long term.