Many early stage startups that need an investor presentation do not have a proper logo and graphical identity yet. Is this a bottleneck for a presentation?

Not really. I do not believe that you need to put your logo prominently on every page of your presentation. Hence, it is not very important in presentation design. The most important design element for a presentation is color. The color scheme will decide how your slides look.

So, pick a color scheme you think is appropriate for your business. It can be done very quickly. Every investor will forgive you if you decide to change it later. In the early days, you can simply use a text logo without any design to show your project's name. If you are not sure, a temporary project name can be a better solution than a poorly chosen brand name. That brand you chose late at night while brainstorming with the founding team might work great for you, but could be less optimal for your target audience.

Obviously if you are launching in the market than logo, identity and picking the right color becomes (a lot) more important.