Anytime I want more gpu performance all I have to do is plug my laptop into its gpu dock on the desk that also gives me a bunch of extra IO or use my desktop. Not sure why, but you seem to think money is the only factor in choosing a system. Some of us have enough money to buy what we want and benefit from it.
In a year or two I'll sell my blade for around 1500, and replace it with something better. Meanwhile your 2080ti will have depreciated to around a third of its RRP.
I'm not saying you made a horrible choice -- I like the RB, and I really like what they're doing with it -- but you're way understating the cut in performance for the LAPTOP aspect of it. The reason I'm talking about $ is because that's a good way to generalize what kind of performance you COULD have with a non-laptop. I am all for spending ludicrous amounts of money for high end gaming experiences. (and btw I sold my e-gpu solution a little over a year ago and put that GPU in a rig).
So let's play out your scenarios here:
option 1: E-gpu:
$2600 + $300 for enclosure +$900 3080ti (let's just assume it will be there) = with a 25% slower proc and a 10% thunderbolt/egpu port penalty $3800 for a machine that's 15% slower and ur stuck on a desk and you're on a 15" screen unless you spend even more on a monitor.
option 2: sell and buy another blade
$2600 initial -$1500 sale + $2600 for another blade with a 3070 = $3700 for a 40% slower machine
Option 1 for a desktop
High end: $2600 initial - $400 cheap sale of 2080ti + $900 3080ti = $3100 for a higher end gaming experience from 40% to 10% faster depending on above.
Option 2 (midrange)
let's say $1500 Sell the 2080 or the 2070 super - $300 +$900 buy a 3080ti +$250 for a ryzen 4600 = $2350 for a better gaming machine
So even worst case scenario it's still not close. And if you spend the same amount of money on a desktop, you get MUCH better gaming experience, and if you want the same gaming experience (or slightly faster even) you can have it for roughly half the cost.
now multiply that difference across the next 20 years of your gaming career and that's alot of money to spend so you can sit in front of a 15" screen with 2 little hairdryers attached to it.