His implication is that 'Teiku' is a non-answer. If we don't know the answer, we throw up our hands and say 'teiku', which leaves the question open. This understanding is corroborated by the myth that I grew up with, namely, that 'teiku' stands for 'Tishbi yetareitz kushyot ve-ibayot" - 'Tishbi (i.e., Elijah the Prophet) will answer challenges and questions'. The implication is that our knowledge is insufficient, but at some point the tools for discovering a correct answer will be restored to us.
That's not what 'Teiku' means. It most probably is a derivativr of the Aramaic verb 'to stand' (kah), thus 'it will stand', or to the Aramaic verb for weighing (tkl), thus, 'it is balanced'. Either way, the implication is that we have arrived at a stalemate, which is an endgame scenario. Teiku answers the question; the answer is - there is no way to have a definite outcome; tie; stalemate; deadlock. Modern Hebrew reflects that - the term for a 'tie' - like in a soccer match - is 'teiku'.
There's much evidence for this - linguistic, the context in which it's used in the Gemara, and the contexts in which it's not used in the Gemara. Rambam always paskens a 'teiku' as a 'safeik', but often will take a side on an 'ibaya de-lo ifshetta' (unanswered question), which means that he regarded teiku as a bona fide psak. Furthermore, the Taz holds that 'chisaron yedi'ah' (lack of knowledge) doesn't qualify as a safeik - important lesson there: no excuse for doubt that arises from ignorance.
The danger of the first (wrong) position is that it's a cop-out. We don't have access to the answers. We forgot. Woe is us. We're ignorant. Let's rely on a miracle. It's the ultimate in lack of self-confidence, and it's not a way to proceed through life.
The other (correct) understanding acknowleges that there are some questions that simply don't have cut-and-dried answers. Sometimes there are claims that compete with each other in an irresolvable way. Instead of copping out of a difficult situation, the Gemara acknowledges the validity of both claims and declares a stalemate. It's an exercise in true intellectual humility, not this self-effacing pious garbage that sometimes passes for it.
R' Matisyahu stated that teiku is 'a wonderful answer'.
'Hilchesa kavasei ve-lo mi-ta'amei' - he's right that it's a wonderful answer, but he's wrong about what that answer is.