Another one: they conflate Type and (Locator) Instance in a unique way that just about nothing else in TS does. Those are two very different things with the same name with Typescript's (antiquated) enums.
There are too many ways to accidentally import/redeclare/rescope the Type of an enum so that TS "knows" the Type, but because that type (generally) has the same "name" as the most likely (Locator) Instance it assumes the same access applies leaving runtime errors behind when that Instance isn't actually imported/available. Typescript has no easy way to tell the difference between access to the Type isn't access to the (Locator) Instance (nor vice versa). Reasoning about those runtime errors or preventing them is additionally tough for people too because of the same "name" problem for two different things.
This is something that's painfully hard to avoid in cases where you are trying to encapsulate an API's Types separate from its imports/exports because they might be introduced or manipulated at runtime (plugins, sandboxes, proxies, etc). Unfortunately, this is also too easy to accidentally do even when you aren't intentionally doing something complicated like that (trying to generate automated .d.ts files in a bundling toolchain, for example, when APIs are in the boundary space between unintentional public API and internal tree-shaking or optimized symbol renaming).
Let's turn it around, union types are so much easier to use and so much more powerful. Enums have only a small subset of the features, are not compatible to JavaScript code and are hard to understand (read the docs about type script enums and you will see).
To be clear, this kind of structure is only emitted for numeric enums. String enums with explicitly declared static values are roughly equivalent to the equivalent Record<string, string> (runtime) and a corresponding type T[keyof T] (type check time).
IME, most of the complaints about enums apply only to numeric ones.
The major exception to that AFAIK is the fact that enum members of any type are treated as nominally typed (as in A.Foo is not assignable to B.Foo even if they resolve to the same static value). I am among the minority who consider this a good thing, but I recognize that it violates expectations and so I understand why my position isn’t widely shared.
