These are also the most commonly used plastics in plastic bags and various containers used for household products. Plastic pop bottles for example are made from PET (polyethylene therephthalate) which is a variant of polyethylene and thus contains only C, H and O atoms. Same thing for HDPE, LDPE, PPE etc.
So incinerating them in a powerplant or other facility that has an efficient incineration process with good filters to catch any soot created from inefficient incineration can be a good thing.
Whether this is better than recycling the material depends on how well sorted and clean the plastic is.
I wrote my M.Sc thesis in environmental economics on the subject of soda bottle (PET) recycling. Examining which option was the most environemntally sound. I found that for PET bottles recycling or reuse was preferable to incineration. This was due to the fact that the deposit refund system gurantees that other types of plastics are kept out of the system.