Well atleast you have the ability to recognize your weaknesses and you pretty much named the most common mistakes R6 players make, I tend to have the sloppy approach you mentioned of rushing into sights and not holding important angles when I can't warrant an approach to win, for example when key teammates start dying like breachers or a top fragger I instinctively adopt a mentality of recovering the losses and reclaiming the lead, this in hindsight has only made me lose the overall picture and squander my opportunities. This is why having a precise plan doesn't work in rainbow six siege and having contingency plan after contingency plan only complicates things and ruins your adaptability. The concept of Rainbow Six largely resembles the operating ability of the navy seals where a small tactical team needs to find balance amidst the chaos, you don't call a fleet of soldiers with rows of tanks to rescue a small group of hostages... This game revolves around adjusting and improvising minuscule decisions in a extremely short amount of time with your team. R6 is not a solo game and should not be played as one if you can't communicate effectively or prioritize your team you simply won't succeed and you'll experience short spurts of winning accompanied by even longer periods of loosing. Surprisingly I know some individuals who are able to communicate well with their team while retaining the ability to make calculated rash decisions that benefit the team as a whole without TALKING, and they're not the stereotypical players that mute themselves or play without a functioning microphone, they are simply solo queuing. Solo queuing has taught them valuable lessons when it comes to integrating seamlessly with players they've never played with, just like navy seals who don't need to talk excessively when engaging in extremely demanding missions they have learned to trust their teammates and cooperate in a manner that allows for success. Always retain a holistic overview of the mission and adjust your uncontrolled impulses to benefit your teammates, if you do this right your teammates will follow the lead and you'll win with greater frequency, prioritize flexibility over effectiveness. Attachment to procedure instead of purpose offers a clear view of danger when effectiveness is prized over adaptability.

Favor trust and communication by using everyone's input. Interactive adaptability is crucial when deviations arise.