How could something agreed upon be theft? If you know the inflation rate for ever, you agree on a possible (but not necessary) loss of value. It makes fiat inflation really different from Monero inflation. Another innovative way to manage this with a predefined inflation rate is to use two units, one being the currency as usual, the other being the currency corrected from inflation. I only saw that in this "relative theory of money", only in French at the moment:

Sommaire — Théorie Relative de la Monnaie v2.718

It's being experimented with an actual cryptocurrency:

Duniter | Home

Duniter is a blockchain software powering the Ğ1 libre currency.

You seem to need to study more Monero. "Monero's inflation through tail emission is designed to go on forever. Starting from mid-2022, Monero implemented a perpetual tail emission with a fixed block reward of 0.6 XMR per block. This results in a continuous issuance of approximately 157,680 XMR annually, indefinitely."

It's maths. Fixed emission per block forever makes relative increase of money supply tend against 0 (0%). 157K/18M=0,87% In ten years, 157K/(18M+157K*10)=0,8% Etc.

Maths? What's that? It's only NGU theory here!