It depends.

TBD is one approach for developing a feature.

There are pros and cons, and they vary with the situation.

E.g., if I were making major changes I would not use TBD. Instead, I would pull changes from trunk frequently, but I would not merge my changes to trunk until they were passing their tests. Otherwise, you "break the build".

One of the criticisms of feature branches is that you delay integration. That is not true if you frequently pull changes.

Another criticism is that if several people are working in feature branches, the branches can diverge. That is a valid criticism, but there is an easy way to mitigate it: the tech lead should know what people are working on!!!

TBD is great for incremental changes.

Another disadvantage of TBD is that the trunk tends to become cluttered with feature flags, making the code difficult to understand, and increasing of introducing security issues.

There is no "best way". There are pros and cons that vary with the situation.