Not at all.

The effectiveness of a vaccine is related to the effectiveness of the bodies immune response to the virus.

As long as different mutations do not affect the effectiveness of a given immune response provided for by a vaccine, that vaccine will be effective against those mutations.

Mutations can affect many aspects of a disease, and often this means a different level of effectiveness of an immune response, but it really does depend on the specific mutation.

For now, there are no selection pressures on different strains from vaccines; it will be interesting to see what mutations become prevalent once testing of vaccines starts.

Why does it take so long to develop a deactivated vaccine version of the virus to teach our immune system what to attack?

Safety. You have to understand what 'deactivated' means for this virus, and that people won't get significantly sick if you feed it to them. That takes time.

While this is not exactly a direct answer to your question, these pages may be helpful:

https://shotofprevention.com/2018/03/14/how-flu-strains-are-...

https://www.cdc.gov/flu/about/viruses/change.htm