The idea is that UBI would give people time for the working class to pursue passions, spend more money, and enable more people to pursue entrepreneurship in the country. All things that in turn would benefit society and the arts.

Then UBI amount is increased (hopefully fast enough) to fight inflation

continues the endless inflation

UBI would likely lead to a decrease in wages or at least a period of stagnation as it would be less important to employees. As far as I've heard long run it shouldn't hurt

It's more that UBI is just not financially possible for any country.

I live in a country with the highest tax rate on the continent and with just 20% of our population as pensioners, the situation is just getting worse and worse even though 49% of the population has a tax rate between 25 and 50% (+13% from welfare taxes). Just with this small percentage, we are spending 20% of our budget in pensions. More than any other area by at least 5% of our national budget.

If the state now had to pay an UBI to 69% of our population on top of this, the very minimum to pay off the UBI without going bankrupt would be to sell off the free healthcare and public transport in their entirety. And I'm assuming a small UBI of 500€/month (Not even enough to rent a 1 room appartement with utilities in some areas).

UBI would destroy any country's budget for what? Landlord increasing rent to match the UBI, corporations increasing prices to match the inflation and people wasting that money when it could have been put to use to increase renewable energy production, improve education, ...

UBI is only a good idea in paper and you only need to look at the public expenses of most European countries + have a basic understanding of capitalist greed to see it.