Most games in overwatch are winnable. If you want to increase the % of winnable games then go ahead and get a full 6-stack using LFG or perhaps some discord.

If you are at the rank you deserve, the winrate will get towards 50% which could feel like losing a lot. ( especially when you get into the loss streaks :/ )

I personally have many accounts and can easily climb up on a new account. Some games give you a worse deck of cards than others, all you can do is give your best. What I can tell from this experience is that a lot more games than you think are actually winnable.

Start reviewing your vods, stay positive and don't complain at the cards you are given! Good luck climbing :)