I wouldn't select a bike by the saddle. Saddles are available in all price categories and all shapes, and they can be easily replaced. If you find a bike you can always replace the saddle later on if it's not comfortable.
I have just bought a new bike, so I've been through the struggle. I am a very experienced cyclist and use the bike as my only transportation, so I know what I prefer. I think in your situation you need to try out a few (maybe borrow from friends for a while?) to find out what you prefer. And if possible, buy used, like everyone has already suggested. I wanted to buy used as well, but I couldn't find what I was looking for, so in the end I bought new (this one:
https://fietsenconcurrent.nl/media/wysiwyg/Batavus_Hommage.jpg a classic light weight steel city bike). Personally I'm not a fan of hybrid bikes, Different bikes cater for different situations. Hybrid bikes look cool but I don't think they're very suitable for city use.
The first thing a good shop needs to do is find out your frame size. There are standard tables for height / frame size, but the length of your legs is actually more important than your body height. You might need a smaller or bigger frame than a standard table might suggest. This is also helpful to know if you're looking for a secondhand bike. Frame size is the one thing you can't change on a bike.
How much weight do you want to be able to carry? Cheaper bikes can carry about 15kgs. In the medium price range bikes can often handle 15-40kg, I went for a bike that can handle an extra person riding on the back. That's because my s/o and I do that often. It comes with a price tag, so if you're only going to carry around the grocery shopping there's no need for an extra durable (and expensive) frame. Some bikes have a rack on the front. For me this is uncomfortable, other people swear by it. it's something you need to try out before buying.
I disagree with the no-kickstand idea. A regular kickstand weighs very little and if you're just going to use it for small errands, the extra weight doesn't matter. You're not in the Tour the France, you just want to be able to park your bike conveniently. My lock is at least three times as heavy as my kickstand. I really hate people who don't put their bike on the kickstand in a bike parking rack. That bike is guaranteed to fall over when you try to park your bike next to it, or when there's a gust of wind. If that person wants to risk damaging their own bike, that's their choice, but I'm not going to be happy if it falls on top of my bike and damages mine. Bikes falling over on top of each other are the nr. 1 cause of damage to bikes.
Do you want battery operated lights? I think a battery is definitely the best / safest option for the back lights because it stays on even when you're not riding your bike. For the front light, a hub dynamo is a good option as well. The problem with battery operated lights is that people forget to turn them off and batteries die when you least expect it. A good solution is to put a replacement battery in your saddle bag. I know these are tiny details, but people riding without proper lights is a bit of a pet peeve of me.
How many gears do you want/need? I think you need to try out a few bikes to find out. I live in a flat landscape as well, but I prefer to ride in a higher gear. That's just personal preference, I have very strong, well trained legs. I think for the average person in a flat landscape 3 gears is probably all you need.
For safe riding and low maintenance I prefer a chain guard. A non-exposed chain will hardly ever drop off. A chain exposed to humidity will rust. I have always had completely closed off chain guards on my city bikes and I can't remember the chain ever dropping off. It's a regular problem with my road bike. As for brakes: I prefer rollerbrakes. Hydraulic brakes work perfectly, when they work, but they are easily damaged. These days many bikes are sold without skirt guards, but they are important for safety, especially if you're going to carry around stuff.