[WP Smush Pro] Wp Smush Pro extensively slow


We planned to use the WPMUDEV Subscription for Websites of our clients. As an agency we are aware of performance is very important.

We are very disappointed about how slow WP Smush Pro is working. This comes that a customer refuses working with his new website we build.
After hours of researching solutions, disabling plugins and endless test runs uploading images we found the following facts.
We show the most important ones here:
*** Test Cases 51 Images, 100MB
** Upload with Wordpress (Wp Smush Pro is offline)
Time used for upload: 11min 1sec’ / 7.75 MB/sec

** Wp Smush Pro Batch & Yoast SEO enabled
Time needed to Smush images: 55’
==> Total time needed for 51 images (100MB)
Upload & WP Smush Pro = 1 Hour 6min 1sec'

** PlugIn EWWW Image Optimizer &. Upload Wordpress
Time needed for 51 images (100MB): 12min

What did you say about this?
Have you same performance measurements?
How can we cancel the subscription since this becomes useless for us?

Thank you for a feedback and kind regards