Well, at it's most basic it's not really that complicated.
Low charges (0% on contributions and the lowest possible annual management charge - ideally as close to 0.5% as possible perhaps) and a decent range of investment options/funds is what you and employees want.
The more generous the employer matching/contribution the more attractive it is to employees as part of an overall remuneration package.
And, in most cases, especially for those with several years to retirement and even those who are older but expect longevity into retirement, they should probably be mostly or fully in equities.
Others will try to make it more complicated, but fundamentally it's not.