Yes, I have also learned that RV salespeople are not very knowledgeable, but I don't blame them for that. It's impossible to to know every feature of every model of every year of every class. They are also quick to show you the larger more expensive rigs. I told one salesperson I wanted a 32' fifth wheeler and he looked at me with a surprised look and said "Why so small? You'll never find something that small." .......whatever
My best suggestion is to do all your homework ahead of time. Most manufacturer websites show all the models, floorplans, specs, photos, etc. You can even download full manuals. Don't rely on the salesperson to tell you anything helpful or technical. He/she will just tell you what you want to hear. ("Absolutley!!, No Problem !!!, These never come back on warranty !!, You're 1995 Chevy S10 will pull a 42' toy hauler no problem !!, etc)
Having said that, don't rely 100% on internet research. At some point you need to look at, touch and feel what you've been drooling over online. Don't forget about RV shows in your area. This is a great way to get out and look at many different rigs without the sales pressure. Whenever I go to an RV show, I'm always with a tape measure and small flashlight and I can go through these things with a fine tooth comb.
Also, if you have zero'd in on a particular manufacturer. Sign up to the owners forum of that manufacturer and start reading. You'll get more real world feedback from actual owners.
Also, don't forget about Youtube videos. Just do a search for the models you are considering and there will most likely be a ton of dealers who do "walk-through" videos of the coach pointing out features. Even if you tune out the sales pitch of the video, it's at least a chance to see the rig close up before going out to the lot to put your hands on it.
Don't let the salesperson sell you an RV, just let them be the person you negotiate with. Try to get 25% to 30% off MSRP. If you can't get the discount you're looking for, try to get accessories thrown in for free (2nd air conditioner, RV cover, bedroom TV, etc.)
Good Luck.