Recently, the group has been discussing block builders and bundles again.

To put it simply, retail investors just need to know that "there is an intermediary layer that can choose transaction order, and you might be front-run or sandwiched," and that's about it.
Don't immediately push yourself to become a half-MEV researcher...
Personally, I remember three things:
Don't go naked on chain with large transactions (split into batches / limit slippage / use reliable routing),
Don't blindly trust the "smart money" label of a certain tool,
Recently, some people have also complained that the label system is lagging behind or even can be misled;
And also, when you see anomalies on-chain, don't rush to follow, listen to them as noise first.
The atmosphere in the group chat is quite genuine:
Half is about popular science, half is about joking,
Anyway, don't treat any KOL as an invincible golden ticket.