As the term "DeFi" suggest, the whole idea behind the creation of crypto and especially Decentralized Finance is to empower the individual user to take control and not to rely on any third party to interact with financial applications. There should be no middleman, no information barriers, no "only for accredited investors" label. Everyone with a wallet can interact directly with the protocol and perform the actions directly, be it lending, borrowing, trading, etc...
While this brave new world in theory is very appealing and got a lot of attention since DeFi summer in 2020, not every protocol or blockchain is really as decentralized as they proclaim. As life taught us, there is no pure black and white out there but many shades of grey. Some protocols present themselves as decentralized but the controlling governance tokens are held by some few individuals that can control the fate of the users funds. Some blockchains call themselves decentralized but the consensus mechanisms are controlled by a handful of nodes. Even tokens like USDC and USDT are not that decentralized as you may assume as real legal companies have issued them and can freeze your funds whenever there might be a reason to do.
As becoming fully decentralized is a desirable goal, the path there is long and burdensome, and not everyone will care about decentralization if this means higher costs or slower transaction speed.
Thus, the term "DYOR" - Do Your Own Research - is ubiquitous as users need to decide and judge on their own how much decentralization is really incorporated into a protocol and if it is worth using it if fundamental values of crypto are not taken care of.