Sinner's was the first of two high-profile cases in tennis in quick succession, with women's world number two Iga Swiatek handed a one-month suspension in November after a positive test for the angina medication trimetazidine.
"Simona Halep and Tara Moore and some other players that are maybe less known that have been struggling to resolve their cases for years, or have got the ban for years," added Djokovic.
"I would like to see, I don't know if it's even possible, the ATP to provide legal teams for everybody, good legal teams, that everybody has to use, be that Jannik, be that Tara Moore when she was banned or Mikael Ymer when he got banned.
Speaking at the Qatar Open, 24-time grand slam champion Djokovic said: "There's a majority of the players that I've talked to in the locker room, not just in the last few days, but also last few months, that are not happy with the way this whole process has been handled.
Meanwhile Britain's Tara Moore, a far less well-known player, was suspended in May 2022 while an investigation lasted 18 months before an independent tribunal determined that contaminated meat was the source of the prohibited substances she tested positive for.
