Some people do less good deeds because of bad health, weak, low motivation and other issues and problems so they will recieve less in Jannah because they did less good deeds. Some people will do alot of good deeds and will recieve higher level jannah because they had good health, strength, high motivation etc so do you think its fair those gifted with good health achieve more? when it comes to doing good deeds.
The One Who decides is Allah, the Al Just. But to help elaborate on the topic, Do you think that reward is based on what you were able to do, or what you weren't ?
For example, which is more nobel to donate 5 dollars when you have only 5 dollars, or when you give 100 dollars when you are a millionaire ?
And We place the scales of justice for the Day of Resurrection, so no soul will be treated unjustly at all. And if there is [even] the weight of a mustard seed, We will bring it forth. And sufficient are We as accountant. 21-47
Please consider the following Sahih hadeeth:
Abu Huraira reported Allah's Messenger (ﷺ) as saying:
There was a dog moving around a well whom thirst would have killed. Suddenly a prostitute from the prostitutes of Bani Isra'il happened to see it and she drew water in her shoe and made it drink, and she was pardoned because of this. Sahih Muslim 2245 b
And Allah knows best
It says in the Qur'an (2.286):
Allah does not charge a soul except [with that within] its capacity. It > will have [the consequence of] what [good] it has gained, and it will
bear [the consequence of] what [evil] it has earned.
So Allah takes your circumstances into account. So your assumption is not true.