No, you cannot climb Kilimanjaro without a guide. You still need a guide to climb Kilimanjaro. That is the law, and Tanzania relies on Kilimanjaro tourists for revenue. In terms of technical difficulty, a competent alpinist might climb Kilimanjaro without the assistance of a guide.
Climbing Kilimanjaro requires the assistance of an official guide. Although, in terms of large mountains, it is not very tough. Despite the fact that it is 19,000 feet tall, the oxygen level at the peak is just 45 percent of that at the base. Hypoxia (loss of oxygen) and altitude sickness are possible side effects. These might range from inconvenient to fatal. Because of a scarcity of oxygen, half of the climbers give up. Hypothermia is a constant danger. The ascent to the peak is difficult and rough, and it is frequently undertaken in the dark in order to catch the dawn. Without a guide, summiting is risky.
Technically, you could, as the climb or trek is rather basic and follows well-marked paths.
However, visiting the national park requires the presence of a qualified domestic (Tanzanian) guide.
So, in practice, you won’t be able to since you’ll need to be accompanied by a guide.