How to avoid CSGO servers filled with bots?

A) Stop searching.
B) Use the community server browser.

Search for classic casual (as it is quite crowded usually) or just simply go competitive mode. The latter is superior to every other mode (the essence of counter strike), teh only downside could be that you really need to commit your time to it as penalty for abandon is pretty harsh.

Bot is automatically filled out when a new game is created. Bots will be kicked out when new players join in through server searching.

It is normal on official server. If you run into this alot, you need to upgrade your internet connection.

I solved that by increasing the max acceptable ping in Game Settings. The ping may be high when you join the server but it goes normal after a while. Probably that's why it was filtering out most of the servers.

Community quickplay is hit or miss. Just use the community browser like everyone else has been doing for the last 20 years. Sort by number of players. Boom.

Community servers - depend on config - you can list them sort by ping and check which will be best for you (check not-full, have players and without passwords)... For others you can increase max acceptable ping (probably you have limit it too low and there are not many servers with players). If you play longer the same game at the same official server - number of bots decrease and increase real players. But on that official servers people often join, or disconect, when you play match after round/2 etc.

Usually before "Joining match..." while the game is loading you can see "Creating match..." (maybe it's a different translation), this means that you'll be the only one in the server.
By the way community servers are better :3