How to get good at Powerpoint?

Download the wall street prep quick access toolbar and use it whenever possible. This alone will increase your speed substantially.

Also try to use the mouse less (for example, instead of dragging shapes to align them, just click them to select and then use your QAT shortcut to align).

I wouldn't recommend paying for any PowerPoint courses. You can learn anything online for free. I would recommend going on company's websites and finding their Analyst Day Presentations. Take note on how they manage the narrative reporting, how they organize their slides and how much space they use or don't use. Then just play around in PowerPoint. After you make a hundred decks you'll get used to the functions and develop your own narrative reporting style. Every bullet point should have a purpose. Every chart should make the bullet points easy to see visually. If a bullet point or slide creates more questions than it answers, then you messed up. 

Just like in the gym, reps.  Make yourself uncomfortable and learn a new shortcut everyday then make a habit of using it in something every day for a month even if you just create a ppt to practie that in.  

I never understood this “PP skill set” from IB guys.

I have now worked for three institutional shops and each we just had a template. What is so fascinating about PP skills that needs to had? 

A part of it relies on creativity and the other on understanding the robust optionality in PPT. I'd recommend becoming comfortable around slide master/manipulating shapes/text/formatting via alignment, effects, etc. As mentioned, it's all about reps. If you're committed, even attempting to recreate visuals/slides will be helpful. From my own personal experience, PPT is massively underappreciated (thought it was a waste of time in IB, but have been complemented tremendously on the skillset and output). Your data/analysis/underwriting can be spot on, but a visually appealing end product will always be more appreciated -- not overbearing to where you're wasting time/effort as there's a balance to be found.

My slides got immensely better once I started being more creative with how I summarized information in graphics. Go out on a whim and create your own visualizations that fit in with the template but also are unique and visually appealing. The best way to do this is by using shapes and playing around with them. Imo being good at PowerPoint really comes down to summarizing important information in an appealing way. Use shapes, use shades of colors, combine shapes, maybe add shadows to certain shapes to make it look nicer etc. Another way to get better is by looking at other decks and combining what people did on those and branch your ideas off of other peoples work

any large institutional shop will have graphic designers designing templates. I'm at a 2nd tier company and even then we have like 20 templates that are professionally designed 

A way for making a good PowerPoint presentation:-

Make it easy. 
Reduce the amount of text.
First, make a content plan.
PowerPoint Designer can help you to get new ideas.
If you're out of design ideas, try using PowerPoint templates.
Use the Slide Master to create your presentation.
Choose the right Fonts.
Create Slides for a Variety of Audiences.
For more learning use youtube.
 

Other comments mostly head the nail on the head. Just look at some other companies' pitch decks (pretty easy to find with some company-directed searches) and take inspiration to build your own templates. Echoing the sentiment that you probably won't need a course (honestly depending on where you work you only really need bare-bones understanding) and anything you have questions about is more than likely on youtube.