@Kegas I've no idea if you're still reading as you haven't posted in ages, but it may he helpful for you & DH to actively consider what 'success' looks like for you. Is this different from 'high achieving' or the same? Is it based on being academic? Being widely read & having a massive spread of interests & general knowledge? Is earning lots of money your only metric for achieving highly? Does participating in a competitive sport at a national or international level come into it?
And what is success? Is it completely linked to your answers above? Or is it finding the unique interests that someone has as an individual? Is it developing them to the best od their ability-even if their ability is average or lower? Is it about having good social skills and being a good friend & kind to those who aren't friends or who are demonstrably different from themself? Is it about being resilient in areas they find a struggle, but putting in high effort & being persistent anyway - even if they will never be top of the class? Is it about trying enough creative & sporting activities to identify something they LOVE? And something THEY feel good at? Is it about finding a community around you of like-minded people & contributing to that community to help you feel good about yourself & give back, rather than only doing things that benefit you as an individual?
If your only definition of success is high schoolwork achievement & landing in a high earning career, then your child is far more likely to be a disappointment to you & not "successful". As others have said, they will pick up on that (if they haven't already) and it will result in some significant development problems for them!
It's been pointed out already that your child will have spent 2 of their most formative toddler years with lockdowns & lack of social interaction going in around them. What did that look like for them? Are you key workers & they continued in nursery/at childminder with other children throughout? Did you both 'high achieving' wfh full time for the duration? Did you already have a live in nanny so their care wasn't disrupted? Or (like most of us) did you have to rely on electronic babysitters to pick up some of the slack to make work commitments possible? Or was one of you a sahp, or furloughed, so they were lucky enough to get loads of direct input from a parent throughout that period-but it naturally focussed on what that parent is interested in & good at? At 6 this whole generation has an array of (very different!) development gaps - please support that rather than writing them off!
Can you check yourselves now and put some steps in place to help your child find their own successes? You say they are 'below average' in sports - in Year 1 I don't know many schools which report progress or provide the opportunities to tell this, so is that based on you trying to hothouse DC in a sport one or both of you excel in? If they're not a young Messi/Jonny Wilkinson/Michael Phelps at 6, maybe try them in karate, or street dance, or trampolining or tennis or ASK them what they'd like to try instead - so they don't have to suffer every Sunday with you two on the touchline telegraphing your deflation in them!
Also be very aware of the conversations you have within earshot of them on playdates, especially if you naturally gravitate towards being that competitive parent who always compares notes with other Mums. I know far too many Mums who have talked about 'X's lack of confidence at leaving me to join in at the start of blah activity' or 'Y's struggle to settle if the class teacher isn't there & it's a supply teacher/TA/cover today'. Funnily enough the children DO earwig in & absorb these opinions about themselves & it multiplies up!
So see if you can take a step back & think about whether you can help your child to develop some interests of their own, and support them in trying a wider range of activities outside of school until THEY find something they feel good at & enjoy doing. It might be drama, music, gardening, cooking, knitting, cubs/brownies, watersports, litterpicking, choir, who knows?... do they have the space & opportunity to try enough different things to find out what they LIKE?
If you've been too busy trying to make them into a cookie-cutter version of yourselves, they might not even know what they like or what they're good at yet - let's face it, at 6 there's still a bit of runway to find out! Help them in that...