Depends on what mode you’re playing.
Primarily, there’s casual matchmaking, which actually is full of new players. Sadly, especially in off-hours, there’s also a lot of bots hosted by some mentally unstable script kiddies (no joke, they buy in a bot hosting framework and just pop that on a VPS somewhere) dedicated to ruining the game for everyone with aimbots, mic and chat spam etc. They abuse the fact that Valve hasn’t updated the anticheat in what feels like years. Regardless, there are still tons of healthy games to be found and bots usually are kicked within seconds.
Additionally, there are community servers which, depending on the actual community playing there, can have bonkers veterans or absolute noobs. These servers often are modded, too.