Buying new is fine as long as you plan to keep it long term. Trade sell in 2 years you will get screwed. Keep it for 15 years and depreciation does not come into play.
Buying used is not the cure all for buying an RV. It does reduce depreciation however it has its own set of pitfalls.
Buying new you can have the exact RV you want equipped exactly how you want it.
Buying used you must settle for what someone else selected.
Buying used you inherit someone else's problems, you have to sort RV out and figure out what has been neglected. There is currently a thread concerning dump valves on a used unit that had been altered.
Lastly there is very little warranty buying used vs. a full bumper to bumper warranty on a new unit. New units warranties can be for up to 2 years.
I'm not suggesting buying new is better than buying used. Buying used can be beneficial just beware buying used comes with its own set of pitfalls.
To the OP the mousetrap is constantly evolving. At some point you have to do your research figure out the features you want and be happy. Next years model will always have a new gizmo. Most cannot afford to constantly trade in to have the latest feature. YOu mentioned you liked the 2017 models. What happens in 2018/2019 you will be lacking features again.
Keep what you have. Don't be afraid to modify it to your liking. Once you get a fews mods done you won't be so quick to trade it in.
19'Duramax w/hips, 2022 Alliance Paradigm 390MP >BD3,r,22" Blackstone
r,RV760 w/BC20,Glow Steps, Enduraplas25,Pedego
BakFlip,RVLock,Prog.50A surge ,Hughes autoformer
Porta Bote 8.0 Nissan, Sailun S637