72 here. My knees are not bad but I try to ride without overstressing ANY body parts. In my hills and mountains the climbs stressed my knees and hips, skeletally speaking (leg muscles and aerobically, too).

You asked if technology has changed in your absence that renders it obsolete = obviously not. But,.....a new e-roadie with 38mm tires and all the advances will make it a totally (enjoyably) different experience from what you ride today. Why? You can ride further with more fun and arrive at the destination with energy. The wider tires make the bike smoother over rough or loose surfaces.

Mine is set to the EU standard of 20kph (no throttle), so assists starting from a stop-to-speed and for hills or when one's legs have been exercised a bit too much. I think $2000 buys an e-roadie weighing 25-26pounds.

Orbea Gain 2020 model with EbikeMotionX35 rear hub motor. Pictured with the 28mm tires it came with. Now on lightweight 38mm tires.
Keep the Trek but don't let it limit your cycling experience. You are worth it.

Size = XL, weight w/o pedals =31pounds


Here's a link to the bike I think is 26pounds, but don't see weight, maybe it was a review - of size Small. $2100. Class3 motor makes it quite powerful.
BTW, not affiliated - nor am I recommending this bike or company. But it is technically different from your Trek.
CF Racer1 - Ride1Up | Best Value Carbon Fiber Electric Bike