It is true that a Muslim is not exempted from the obligation of Salah as long as they are in a stable, sane state of mind. However, they may offer it according to their ability. Allah (Exalted be He) says,
So keep your duty to Allâh and fear Him as much as you can
As for your inability to perform Wudu’ or Tayammum by yourself, you have two cases: (I) You may have someone to help you do Wudu’ or Tayammum if you fear harm due to using water. The person helping you should strike both palms on the dust and wipe your face and hands therewith. Then you must offer Salah, because this is an obligation on you. (II) If you cannot find anyone to help you do Wudu’ or Tayammum you may offer Salah according to your condition without Wudu’ or Tayammum. In either case, you must not abandon Salah. When the Prophet (peace be upon him) was asked about the Salah of the sick, he (peace be upon him) said,
“Offer Salah standing and if you cannot, then sitting; and if you cannot, then lying on your side.”
Al-Bukhari in his Sahih [Authentic Book of Hadith]) (Part No. 6; Page No. 358) It is also related by
Al-Nasa’y through a trustworthy Isnad (chain of narrators) with the addition:
“...And if you cannot, then lying on your back.”
Allah (Exalted be He) says,
And if you are ill, or on a journey
Up to His saying,
...perform Tayammum with clean earth and rub therewith your faces and hands (Tayammum).
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.