The plans are clearly structured on the assumption that’s what would happen—there are separate limits for how much an employee can contribute, and how much an employer can, and the employer limit is significantly higher. Even if an employee wants to max out the plan, they can’t, because their contribution level is capped way under the hypothetical max.
The idea was plainly that employers would contribute heavily to these. Instead they barely do, making them better than nothing, but kinda shit considering how they were supposed to work.
[edit] to put some numbers on it, for 2025 an employee maxes out at $23,500 contribution. Meanwhile, the overall max is $70,000. An employee isn’t allowed to contribute more than 1/3 of the max allowed. In fact, with straight matching only and no fixed or multiplier-based matching from the employer, you can still only hit about 2/3 of the max. It’s hard to overstate how entirely the 401k has failed to achieve its apparent purpose in practice.