Accelerator optimizes content, but if server response is too long, the final speed can be slow.
E.g. here is slow server response:
The page size is only 89KB but is loaded very long - 2.5 seconds (it should be about 0.2 seconds).
In that case we recommend using cloud caching like CloudFlare with page caching: https://support.s-sols.com/help/en-us/1-f-a-q/12-how-to-setup-page-caching-in-cloudflare
Also, it makes sense to clarify such long response from hosting provider.