The people complaining about the Manusmṛti base their accusations on the completely unfounded notion that it is meant for our time. Smṛti means to remember which suggests it's a memory of something from a distinct time. It is still useful because it is still pretty close to the truth and answers some important questions about other texts.
Clues that it is completely not meant for today include:
- Probably the most important. The Sarasvatī river flows clear to see
तं देवनिर्मितं देशं ब्रह्मावर्तं प्रचक्षते ॥ १७ ॥
taṃ devanirmitaṃ deśaṃ brahmāvartaṃ pracakṣate || 17 ||
The region lying between the divine rivers Sarasvati and Dṛṣasvatī which has been created by the gods,—they call ‘Brahmāvarta’—(17)
The decision-makers are somehow able to tell someone's Varṇa, which has been established as very hard to do (although Virāṭa seems to be able to do it pretty well somehow).
The following verse suggests food is free at this time due to the lack of pay or self-cooking. That implies a very different world.
अन्नमेषां पराधीनं देयं स्याद् भिन्नभाजने ।
रात्रौ न विचरेयुस्ते ग्रामेषु नगरेषु च ॥ ५४ ॥
annameṣāṃ parādhīnaṃ deyaṃ syād bhinnabhājane |
rātrau na vicareyuste grāmeṣu nagareṣu ca || 54 ||
Their food should be given to them, through others, and in a broken dish; they shall not wander about in villages or cities during the night.—(54)
(By the way, the first line here misses out some of the Sanskrit meaning. Meṣa means ram/sheep. Anna is used to mean food, but especially rice (kind of like Chinese). So Annameṣa translates as rice and meat of ram/sheep dish, presumably to show the quality of food given. The sanskritdictionary.com definitions for deya and syāt are pretty self explanatory. Bhinnabhājana could translate as broken dish, or it could mean processed food in reference to the cooking and diving process. Thus, I think it means: A rice and ram/sheep meat dish (or a like substitute), [word praising the supreme god in the form of Anna] should be given to them. Perhaps (the person implementing this) could process it. It's safe to say this society is massively more wealthy than our own to afford this and it not even being a big deal to find funds.
Thus, when learning the Manusmṛti discern using your honest judgment what is true forever, what is similar to the truth now, and what does not apply anymore. Also, some verses make it obvious they are supposed to be true forever.
One prominent use of the Manusmṛti is as a companion text to Mahābhārata as many of the terms in the Manusmṛti are used in the Mahābhārata, but with much more of an explanation in the former.
The translation while probably well-intentioned, translates some qualifying terms weirdly, which has a knock-on effect on the meaning of some important verses, so you should look up the Sanskrit yourself. Sometimes it greatly changes the meaning.