The cruise from Traben-Trarbach to BERNKASTEL (beautiful town) and the shorter cruise from Cochem to BEILSTEIN are both good options on the Mosel.
Bernkastel's old-world buildings are quite special:
https://en.visitmosel.de/cities-culture/poi/spitzhaeuschen-pointed-cottage
If you just want an alternative to driving, and you must see Trier, then just take the train, which gets you there very quickly.
Speaking of the train... if you are staying in Cochem, as it sounds you might be doing, and you want to do the Traben-Trarbach > Bernkastel cruise... The train will get you to Traben-Trarbach in scenic fashion. From Cochem, the tracks run through a long tunnel and emerge on the river once again on their way to BULLAY, another River town and minor train hub. In Bullay, the main railway continues to Trier. But to reach T-T, you switch to the Mosel Wine Railway (Moselweinbahn) which hits a couple of other small wine towns on its way to Traben-Trarbach.
After your cruise and some time in Bernkastel, the fast way back to Cochem is a bus + train trip. Bus to Wittlich, train to Cochem. Takes about 1 hour going back.
Moselweinbahn:
https://en.wikipedia.org/wiki/P%C3%BCnderich%E2%80%93Traben-Trarbach_railway#/media/File:Karte_Bahnstrecke_P%C3%BCnderich_-_Traben-Trarbach.png