1: Tiny Viewfinders.
Try to compose an image from the waste with a viewfinder that's a square centimeter, and you will be given a lesson in frustration. The vest pocket, Brownie and bellows camera's popular before the 1920's used tiny prisms for the user to compose the image. Go through any historical archive and you will see countless badly composed off center images due to the tiny viewfinders, even the public back then complained of how difficult it was to get composition right. Add a hundred years of wear and tear and even bright days are like like composing in fog. The image below demonstrates a large easy to compose viewfinder of a TLR Rolleiflex from the 1950's compared to a Vest Pocket camera from 1916.
2: Parallax error.
The terrible parallax error you get from 1910's cameras is related to point one above. Since the viewfinders are tiny prisms, uncoupled and off center from the lens. The tiny image you see is only a rough guess of what will actually appear on the image plane. Unlike SLR cameras which see exactly the film area, or TLR's like Rolleiflex's or Leica's which still have some parallax error but have sophisticated engineering developed in the 1920's to compensate for this.
Sadly these faults, lead to a situation where you line up the perfectly composed shot, as you squint into your tiny viewfinder. After you develop the film you have to put up with disappointment.
3: Light Leaks.
Due to a hundred years of aging and wear and tear mechanical faults are to be expected. The leather bellows on these cameras start to degrade and split open over time, creating light leaks onto the film. Also the springs on the shutter release can stick at the quarter or half way point, again creating uneven exposure.
4: Winding to the next shot.
The winding method takes several seconds to wind onto the next shot. So when you see a moment you get one chance to get it. Also it can lead to overlapping photos if your too anxious and wind the film too fast, or if you forget to advance the film it leads to double exposures.
5: Slow shutter speeds.
The fastest shutter speed on the small to medium size cameras of the period is one fiftieth of a second, so needless to say it does not lend itself to decisive moments, but the blur is part of the charm. The larger 4x5 German press cameras of the period like the Goerz Ango, can have shutter speeds up to one thousandth of a second, but I have yet to find a working model.
6: Light Flare on sunny days.
The paradox of using cameras from World War One is the viewfinders become clearer in bright sunlight, but then due to the poorly coated glass this advantage becomes a dis-advantage when the lens flares and screws with the contrast.
Once you point a un-coated lens towards the sun even slightly the image flare is ferocious, although from a creative point of view it can lead to some cool creative effects.
7: Lack of F stops and shutter speeds.
The average consumer camera a century ago had two shutter speeds 1/25 or 1/50, and then 3 to 4 aperture settings usually F8, F16, F32, F64 so the options for creative techniques and exposure control are extremely limited.
I shouldn't moan, as consumer film now has a whole range of iso speeds. Back then, people were more limited in their film speeds, 100 iso back in the day was considered fast.
8: Scratching of film.
Related to light leaks, the mechanical engineering was not that sophisticated, and after a hundred years degrading moving parts, the film tends to scratch. Some cameras are worse than others, ironically I find the cheap cardboard box brownies are scratch free.
9: The Cost of Film.
When your average 127 film costs €8-9, and medium format on average costs €4. Divide that by 8 photos per roll, 50 cent a photo, then processing costs of 3 films per batch.
Not to mention the price of 4x5 large format photography. Luckily I'm a working photographer so being such an in demand profession in a time when everyone has a camera on their phone, I'm fabulously wealthy, and I might have to forgo buying that extra fleet Porsche's I wanted.
10: Always missing the shot.
I could add several other foibles to this list (like the lack of wide angle lens), but ultimately when all these drawbacks combine I'm always missing shots of moments. I now understand why, when researching archives of images the lack of images and how few images are usable.