I tried really hard to make gaming on laptops work - and the result is that you get a more expensive, less capable machine. You'll end up spending 3 times the money, and are usually left disappointed (I know I was!).
Most vendors will happily shove high end components into a box they know doesn't have the right thermals to keep everything running, so unless you're also dragging a freezer around to keep the thing cool - it will hit thermal limits pretty fast. At which point the nice cpu/gpu no longer matter, and god help you if you actually intend to use it on your lap (bank some sperm - because it will fry yours...).
I can fit my current travel box (mini-itx InWin case, 20 inch display, keyboard/mouse, mousepad, power cable, hdmi cable) in a carry-on sized piece of luggage, with a smidge of space left over.
Yes - it's still a lot bulkier than a laptop, but I can actually play games on it and have fun. Which is not really something my "gaming" laptops ever did very well.
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Bonus - if you retire it after 4-6 years, it makes a killer media pc. Most of my laptops were basically garbage after 3 years (Cheap plastic cases degrade/crack. Screen/keyboard are worn out and not economical to replace. Bad thermals decrease component lifespan noticeably.)
I was lucky and building before prices shot sky high and availability became so limited, so it might be harder to find a card you know for sure will fit.
There's a pretty large community around building small form factor pcs, and a lot of forums will have case/card compatibility lists.
I completely agree with you that laptops degrade way faster than I like