[jfengel]

A lot of sounds are difficult even for a native speaker to distinguish in isolation. That's especially true for plosives, since they can't be held; you have only a moment to hear the difference.

Native speakers have the advantage in spoken conversation. They quickly understand not just the word, but the context. No native speaker would ever confuse "Give that document to Ted" with "Give that document to dead" since the latter is nonsensical. Even if you actually said "dead", most people would interpret it as "Ted" without even noticing anything odd about your pronunciation. (In fact, in a context like that between two vowels, it's entirely possible that you would keep your vocal cords buzzing and produce a "d" even if you'd meant to say "t").

[potiuper]

There are issues, for example: ren[t/d] the furniture.

[jfengel]

Definitely. English is hardly even the worst offender there. I'm learning French, and as a non-native speaker I am utterly lost at anything close to conversational speed. The language has many homophones and near-homophones, and liaison makes word boundaries unclear without context. Get slightly lost and it's all over.

[thaumasiotes]

> and liaison makes word boundaries unclear without context

There's very little blame to be placed on liaison, since word boundaries are unclear in every language, including languages that e.g. don't allow syllable-final consonants. English speakers feel like they have a strong grasp of where word boundaries occur because of the orthographic space, but the space in the writing system does not coincide with word boundaries in the language; it is heavily conventionalized.