I can't speak to ready-made ebikes but from building a couple myself I know that they can be made relatively maintenance-free (of course you'll need to replace

I can't speak to ready-made ebikes but from building a couple myself I know that they can be made relatively maintenance-free (of course you'll need to replace brake pads and tires once in a while, and other standard bike maintenance). For the punctures, get better tires. My personal recommendation is the Schwalbe Marathon Plus tires. They're made to comply with EU standards required for e-vehicles going up to 50km/h (i.e., ones that require a license and inspections). I had three punctures my first year, second year I switched to these and haven't had a puncture in the two years since. The chain falling off sounds like bad workmanship. I had a similar issue with my first bike which was a mid-drive. The motor shifted the chain line slightly outwards, and that was enough to cause drops. I got a new front sprocket that cups inwards to correct the chain line and have had no chain drops since then (about two years also). It's surprising to me that an off-the-shelf ebike would have such issues, it suggests shoddy design work and/or insufficient testing. Loose joints again sounds like a workmanship problem. I'm a software and electronics guy, not a mechanic, but I don't have any such issues on my bike. The first time I mounted the motor I didn't tighten it hard enough and it worked itself loose (still worked, I just noticed that it had a bit of play). Tightened it again and no such issues since. The left crank coming out is not something I've heard as being common on bikes. It's never happened to me in the 15000km I've put on my ebikes, or the thousands I put on it before installing the motor. Sounds like it just wasn't tightened well enough, which again suggests shoddy workmanship. All in all, it sounds like you got unlucky and either bought from a disreputable manufacturer, or you got a lemon. Either that or my amateur builds are much better done than the purpose-built ebikes being sold, but I doubt it.