After a nefarious start (I didn't even wanted to check my K/D ratio to no get depressed) and feeling to old for this shit, compete with 13 year old kids which more time and experience than me (and reflexes), I decided to play CoD on my own style.
Instead of trying to do cool shit: wallrunning, jumping and sliding to get a kill like a pro, I took a more grounded and careful gameplay approach (almost as I was playing a BF game), that is checking for my enemy sounds, aiming while taking corners, cover doors and other openings at the minimal sign of something dangerous, backtracking to safer locations and cover other places (camp if you wish to call it that), use rocket launchers to take down UAV, trying to cover my teamates back, sprint and use boosters sparingly to avoid getting discovered...
And my K/D improved to 1.0, which is nothing exceptional but it has been getting much better and I end most matches on positive while having a good score and helping my team.
I also find that the Matchmaking on TDM is much better than in other game modes, so I focused on that.
The best was when 2 players from my own team saw me I was dominating the match with my tactics and called me a "camper" and started shooting me, they couldn't believe someone lower level was doing so much better than them lool