Observations from yet another terrible talk.
(To protect the guilty, the presenter will be called "Epic," short for "Epic Fail II," and without loss of generality will be referred to with masculine pronouns.)
Epic committed three cardinal sins of presentations (there are more than three and some of the others were present in the terrible talk), in increasing order of badness:
The sin of humming:
"Hum... like... basically..." were Epic's most common words. Or sounds, more precisely, because that's what they are. Sounds that Epic made as his brain composed the sentence that was to come.
This is the main problem of using slides-as-presenter-notes, though it also happens to presenters who have separate "talk skeleton" notes and don't rehearse a few times: bullet points aren't feasible out-loud sentences, so, to unprepared presenters, they act as stumbling blocks rather than helpful hints.
Some people are very articulate; some can be articulate from notes; most of the others need to do at least one run-through of the notes, preferably to camera so they can review it. The camera is essential, as without feedback there's little improvement.
Humming is a sign the presenter didn't care enough for the audience to rehearse his presentation.
The sin of non-preparedness:
Like most presenters, Epic seems to have created his presentation in a small fraction of the presentation time. That's usually a recipe for disaster. While some people can make good presentations impromptu or quasi-impromptu, most presenters should prepare carefully.
Epic's presentation had no clear objectives, no clear structure, and above all, no clear arguments. For comparison, there was another presenter at the conference who, in order to explain a programming philosophy created a motivating example based on refactoring a cookbook.
The procedure for preparing isn't complicated: decide what the presentation objectives are; decide how they sequence into each other; devise ways to explain these objectives; assemble the presentation; rehearse.
Epic skipped all these stages, except the assembling of the presentation as a sequence of presenter-notes-on-slides, but without actually thinking much about what each point. Epic didn't think about the phrasing of the points (see previous sin), let alone consider how to best explain them to the audience.
Good presentations begin in the preparation; bad presentations in the lack of it.
The sin of self-absorption:
The audience was promised, and therefore expected, a technical talk about a technical tool. Epic delivered a presentation about Epic: Epic's education (really, a CV slide and multiple name-drops to Epic's school, Epic's degree, Epic's degree advisor); Epic's actions ("I did this," "I found that" not "data show" or "tool does this"); Epic's performance on Epic's job (via repeated references to a sort of limited field contests/competitions, to which the audience groan was the only appropriate answer).
Two other presenters in the same session described highly technical tools, barely ever using the first person, talking about the tools, offering interesting if technically challenging knowledge. That's because, unlike Epic, they understood that the audience wasn't there to learn about the presenters' lives, but rather about the tools.
Epic, like many terrible presenters, bought into the idea that every presentation has to be a story (more or less right, even for a technical audience) about the presenter (absolutely wrong, unless you're presenting an autobiography).
Audiences don't like bait-and-switch: deliver what was promised, not what you like.
Many talks are bad, and that's a choice made by the presenter.