Why does it take extremely long for me to find a game in any online game mode? When matchmaking finally finds a game it then takes a very long time for the game to start, sometimes taking up to 5 minutes or more. For someone who’s time is very limited playing games this is a huge turn off for me when I’m trying to play Halo5. I almost feel like the slow loading has gotten worse. I hope they eventually fix this but who knows the game is getting old now and i doubt 343 really cares. I honestly wish i could play HaloOnline on my PC.
Sincerely- LOST INTEREST
It could be a combination of things like your location, your rank level and/or the population of the playlist when you’re playing.
Taking a long time to start after finding a match is because there’s open player slots. Sometimes they fill and sometimes they won’t. Either way a match won’t start until they all fill up.
Ever since the May 1st Update: I got my Onyx in Elimination…but I really only play Halo 5 for BREAKOUT 2.0 I played 160 games so far… and I get BREAKOUT 2.0 so few times that I’m just done playing Ranked.
I like to consider my self a competitive player however, I have never been good or had the motivation to memorize spawn location and chuck grenades in those spots… and subsequently I am really not pro material. ReSpawning has always been a struggle playing high level players. Teammates spawning nearby and starting to fire their weapons attracting attention to my location has gotten old.
So I have moved my play time to custom games and Social. I have never had a problem getting a QUICK PLAY match before, but now it seems like there are none to be found… I even put my search parameters to Expanded and, it never finds a game. Historically I have always found a game in about 10 seconds, but now NOTHING.
I try BIG TEAM BATTLE and it finds nothing. TRIPLE TEAM is too hectic for me and SUPER FIESTA has always been a place to just play with different versions of guns that are not normally found in games. I always considered SUPER FIESTA a newb friendly gametype. I must have waited almost 14 minutes and no game was found twice.
I cannot speak for people missing ACTION SACK but I can tell you the BREAKOUT 2.0 Community is feeling distraught. It was the only place a player could take the responsibility for their own life. You really had to keep an eye on your team. 
Proffesional Playlists are never going to be as populated as Slayer. MLG was never the most popular gametype but it was very important to the community.