The trick with Tracer is to play her like a mosquito, not a front-liner. Try flanking, going after stragglers, and giving a wide berth to anyone with range-closing capabilities (especially Streetpigs). She’s geared toward mobility and quickly bailing out of hairy situations, so you need to be mindful of your surroundings and stay on the move while managing your cooldowns; you never want to be in a situation where you need to Blink but can’t, and Recall effectively grants you a free do-over every time it resets, so don’t forget about it and use it wisely. The challenge is in mentally juggling all of this while a fight is going on.
The thing to keep in mind is that Tracer has a high skill cap: her effectiveness depends a lot on how smart you are with her abilities (for starters, you’d be surprised how many people are apparently unaware she can Blink in ANY direction, not just forward), so you have to actually know how to use them instead of just spamming like some other characters who will go unnamed for the sake of civility. I find her the most rewarding character to learn how to play and the most enjoyable once you get the hang of her.
Cheers and good luck!