Not only are there no useful effects like lens flare in the most recent edition of iMovie, there is no way to add them or to get plugins to fix the problem. In many ways it is a serious downgrade from the previous editions, taking what could be used for serious video editing and making it essentially an animated scrapbook. It's also much harder to precisely edit clips together. While in this version it is easy to throw a bunch of vacation videos together and mail it to your aunt, one could do that with no issue in previous versions and there was no reason to downgrade. It was exceptionally frustrating to buy a new computer and find that the supposed updated software was so incredibly inferior to the previous editions.
If it were possible to buy effects like apps in the digital store, I would gladly upgrade that way, but in the current edition of iMovie there is no way to upgrade. Not with expansions bought from Apple, not with plugins created by users.

It would be great improvement if this issue was addressed in a coming update or in the next edition of the software.

Later in the feedback form, it posed the question:
What would make you use iMovie more often?
If it worked the way it used to, with clear and precise clip splicing and effects that actually enhanced the movie instead of just inducing headaches.