But Terra did have collateral. Luna equal to 1 USD was burnt (more like locked) once a UST was minted.
The whole conceit of DAI is that instead of burning luna at a rate of $1 they would burn it at a rate of $1.5 , The mechanism is exactly the same! And it will fail in exactly the same way.
DAI has multiple assets, the vaults are at 150% at a minimum and independent from one another and, most importantly, there is no one offering 20% APR on staked DAI. It already went through worse crashes than UST did and it managed to recover.
It's far from perfect, but it is certainly more resilient and has shown to be able to pass the Lindy test.
Iron/Titan did not have any such high apy and still collapsed. In case of terra, I concur that the driving force was the Anchor ponzi, but it was the mechanism that failed.
Iron was explicitly under-collaterized, and it was also trying to lure stakers by providing yield-farming. DAI is the opposite, stakers pay the stability fee to open a vault.
It did have a yield-farming component (you could mint DAI at 1% fee and put it in the DSR that would pay 2%), but that got completely knocked out in 2020. That crash was already a quite expensive lesson (tens of millions USD) for the MakerDAO team, and a lot of the investors had accepted a haircut in order to bring DAI back to the peg.
To repeat: I am not saying that DAI is bullet-proof. What I am saying though is that all the reasons you are using to make your case do not apply to DAI as it currently works.
The whole conceit of DAI is that instead of burning luna at a rate of $1 they would burn it at a rate of $1.5 , The mechanism is exactly the same! And it will fail in exactly the same way.