assuming windows, windows comes with default security settings. neither steam nor the game installer nor the game make any changes nor bypass whatever antivirus, security settings, folder permissions, running programs you have on your system. up to YOU to manage all that for this game and any other game/app you install.

if the launcher does not appear try looking in folder
c:\users\yourWindowsLogin\appdata\local\programs\cd projekt red\redlauncher\logs
try REDlauncher.log but may be an error msg in the others

game needs to create folder
Documents\The Witcher 3
to store your graphics settings in .settings files and save files in the gamesaves folder

is the folder there? if not check windows security/controlled folder access.
if on add exceptions for the game launcher and game

also check your antivirus log. might be blocking game launcher/game
and check your firewall log since the red launcher needs network access.

running Windows One Drive? one drive moves the .settings files out of your
Documents\The Witcher 3 folder so the game has nothing to input.
I do not use one drive so cannot not offer advice.
windows one drive was released in 2007. VERY many websites with
tutorials/manuals/movies/youtube videos written by experts devoted to
One Drive/synching files/using steam, etc.

if after trying all the above and the game still fails,
go to the steam game folder then the bin folder.

run x64/witcher3.exe for the dx11 version
run x64_dx12/witcher3.exe for the dx12 version
maybe the game works but just the launcher has issues.

game requires DirectX jun 2010, vcredist 2012, vcredist 2013, vcredist 2019
which "should" be installed by the game. you can manually download from MS and install/repair with admin permission.
or the files/libraries/installers should be in your steamworks shared folder.

if the games work but not the launcher add to steam launch options
--launcher-skip
and skip the launcher

check windows event viewer and also windows reliability history. might be a game crash event. an error msg would help

IT worked. THX.