Pretty bad when these things happen.
It seems like BalancerV2 was hacked, V3 seems fine. Real OG projects, tens of times audited, open sourced, working for a couple of years already.
Like insanely bad, as in one hand you have the most complex and secure decentralised systems, and on the other hand, there are some hacks. In the first case, people should not use approve modes (sadly that is the way how ERC tokens work), but to have atomic transfer and execute functionality everywhere.
Technically, even in case of web2 hacks, if you put your credit card details in, and some site was hacked storing your data, can start draining your funds, but that is why you have payment providers and some regulations against actually storing any kind of data like that.
So technically, there is a storing of user's fund access keys, which can be used by bad actors. I do not seem like they do some things like that right now, but interacting with DeFi should be atomic.
Another important point to note, is that, most of these hacks would not happen with a better architecture/design of VM and token system. As DeFi developers would not need to use all kinds of complicated solutions for payments and gathering data and execution and whatsorts.
Safe system design is a must to create a safe environment. Let's build more. But more safely.