This information applies to versions 3 and older
Your version of Nik Collection was released before any information about subsequent Mac operating systems was available to the developers, so the error message could not take them into account.
Unfortunately Nik Collection 2018 by DxO and Nik Collection 2 or 3 by DxO are not compatible with macOS Big Sur or newer.
Please click this link to see the compatibility tables for operating systems and third-party software.
In this case, your options are either to purchase the current version of Nik Collection by DxO or to run the version of Nik Collection by DxO that you already own on any of the OSes which are listed as supported.