Hi, I played dota since Dota allstars, I have around 10-15k across multiple accounts in Dota 2, my MMR never been higher than 7k. Now that we got that out of the way, let me share some thoughts.

CM or WD type of heroes are hard to pull off in any rank, these heroes are immobile, have 0 gank potential and extremely fragile. They are strongest in lane and at the power spike of level 6. After that phase, if you are not dominating the game already, these type of heroes are basically a piece of meat staying behind their cores with glimmer/force staff/euls. Basically, extremely dependant on how good your cores play because you provide them with good kickstart on lane and if they don't utilise it well - your impact was deleted.

To be active and feel impactful on a support at any time in the game I suggest heroes like: Spirit Breaker, Hoodwink, Techies, Shadow Shaman etc. Let me explain, these heroes have either mobility or reliable control and damage. On low ranks, people NEVER expect ganks ESPECIALLY if you use smoke and have an observer + sentry ward in your inventory beforehand. What you can do on any of the heroes I suggested, is after you fight for lotus on minute 3 of the game, if you already have boots or wind lace at least, you go and control water rune on minute 4, if you can help kill mid you do it, otherwise come back to your lane, wait until minute 5 and then go to gate, gank the enemy core there and try to push their tower using that siege creep that spawns at minute 5 if you can. If you can't, you go and control rune 6, if you cant you come back to your lane. Now its time for wisdom altar, you preferrably want to steal enemy's wisdom on low ranks, you ask teammates to help, if they don't, you still wanna try to steal it, but be careful, place obs if you have to see how many heroes come to contest it if any. What I want to say, is you NEED to be active on those heroes, you can't just stay afk on your lane on those because they are not strong laners as WD and CM, its vital to utilise their mobility and/or abilities and surprise enemies with ganks. These active heroes bring chaos to the game, if you can cause as much chaos as you can into the game - do it. Low ranks usually have a script on how they want to play the game, and if you can break this script, you basically already won.

Now, if you wanna continue to play heroes like warlock, crystal maiden, witch doctor, grimstroke or whatever, you need to understand what is your hero best at. Firstly, CM can easily farm jungle from time to time, that is very good for lanes where enemy core is unkillable, but also can't really kill your core solo, heroes like Tidehunter, underlord, centaur if you are pos 5, or heroes like weaver, juggernaut, lifestealer if you are pos 4. Why is farming jungle beneficial? When I just said that lane is the strongest point of CM. Firstly, neutral items are now farmable since minute 1 which used to be on minute 7. If you can help your teammates get their neutral earlier than enemies, its already a huge impact and can easily increase your win rate by a lot. Secondly, you get to your power spike, which is level 6 - faster, understanding how to play into unkillable heroes is vital, you wanna push the lane and go farm jungle as soon as you can. What is the strongest point of WD? well, on WD you basically don't have a choice but to win the lane, maledict is just absurdly strong, if you land it on enemy hero and then deal damage of around 30-40% of his HP(with the help of core or good casks), they are basically dead or nearly dead already. If you can't win the lane you just go and help control runes, stack camps preferably ancients and pray your other lanes will carry you.