No, most plans being cancelled aren't worthless. The insurance company is just adding one or more new benefits and adjusting premiums so the plan can be marketed as ACA compliant.
CoventryOne Catastrophic 100% HMO Plan DE
https://www.healthcare.gov/
There are a number of plans that provide practically no coverage but have very low premiums. Since worthless plans have to be replaced with real usable insurance, the premium without subsidies will increased substantially. For example, an individual plan with a $20,000 deductible, 40% coinsurance, and $30,000 yearly maximum out of pocket could be purchased in Florida for about $50/mo before the ACA goes into effect. The replacement plan has a $6350 deductible, $6350 yearly maximum out pocket with a premium of $132. This is a 264% increase in premium. This of course is not a fair comparison but that's how people will report it on the Internet.
Many worthless group insurance plans base premiums on employee turnover. Such plans were marketed by CIGNA and a number of other companies. CiGNA's plan required an average employee turnover of 70% a year, average employee age less than 40, $2000 deductible, 30% coinsurance, and exclusions for maternity, preexisting conditions and hospital admission for the first 6 month of employment. The average premium was about $30 to $40/mo. Some states even allow this insurance to be secondary to other insurance such as auto insurance. So if the employee was injured in an accident,which is the most common major claim for young people, this employer health insurance will probably pay little or nothing.
These plans are sold to businesses with younger employees with high turnover rates. Since most employees of these businesses leave within the first 6 months, claims are rare and profit margins are high. For most employees it's a ripoff. When the ACA is implemented for employer sponsored insurance, this type of insurance will have to be replaced will real insurance and the premiums will probably double. So the headlines will read, health insurance premiums will double at xyz company. What you won't see is the fact that that the company is replacing a worthless plan with real usable insurance.