If you are someone who needs the mobility of a laptop while using it as a docked "workstation" while in the office/home connected to external monitors than Thunderbolt is definitely useful, potentially a "must have".
The ~30% performance loss when using only an eGPU and the laptop screen itself pretty much eliminates any performance benefit you are going to gain from a eGPU with even a 2080 TI. There may still be thermal and acoustic benefits gained, but at the cost of MUCH larger footprint and desk space required.
For many people, like me, who have a dedicated desktop workstation that I use regularly, but are looking for a good gaming laptop to use when I feel like sitting outside on the patio, travelling, or just sitting in the family room so I can watch tv and game at the same time, Thunderbolt looses most of its benefit and I don't miss the exclusion of the port.