Why bikes are automatically terrible if they have a few kgs extra compared to another model.
Bikes are not terrible because they weigh a few kgs more than the lightest, but a very cheap bike will have very cheap bearings, saddle, chain,pedals and wheels etc and for this reason even if it seems ok it just wont last and will require constant work and parts, might be ok as a hack but little use for a cyclist.
Cheap high tensile steel bikes are the workhorse bikes of the world across Africa, South America, Asia etc, bikes like the Buffalo bikes. 26" wheels even single rim are strong wheels especially with a high spoke count. High tensile steel frames and forks will rarely fail even if they have surface corrosion. A 6 or 7 speed chain is a much stronger chain than 9,10,11 or 12 speed because the chain is much thicker. Steel cogs and chainrings are very hardwearing. It's pretty easy to index a 6 or 7 speed freewheel as the tolerances are so wide.
There are lots of positives about cheap bikes with regard strength. Yes in the detail you can get some poor components but I wouldn't necessarily say cheap pedals or saddles are bad.
There are huge amount of compromises made to bikes to make them lightweight, weaker frames, weaker wheels, weaker components in general and safety is often compromised to achieve performance.
Should also be pointed out the efficiency of making such bikes is incredible. Many high tensile steel frames are made in seconds by welding robots. A high tensile steel frame made by fuji-ta about 3 or 4 years ago was only about $4-5 factory door price so efficient to make and fully recyclable. Also steel is the most consistent quality of any frame material. Steel frame production has evolved over a 100 years.
Bikes are sold as working machines in Africa and many other countries, something to take abuse and be worked hard but in western Europe it seems they are sold more as a lifestyle choice or fashion accessory.
Once properly serviced and adjusted these should be very reliable and dependable bikes in my opinion even if they do feel a little bit more sluggish to ride.
View: https://www.youtube.com/watch?v=BMY8NeRFHFU