Since moving from Ferrari to McLaren, Alonso has endured a massively disappointing period, and while progress and improvement have definitely set in, the Spaniard is still in no position to target a Grand Prix victory.
"It's still painful," the 75-year-old Ramirez told Spanish sports daily AS.
"McLaren's evolution is good but it's too slow. They're losing sponsors and will lose Alonso as well. It cannot be otherwise. He is a winning driver and he has to win."
"I don't think he will endure more than next year. I do believe that's his limit."
The legendary Mexican who started his career in Formula 1 in 1961 alongside the Rodriguez brothers, casts an equally disappointing view of McLaren's performance since his former team joined forces with Honda.
"I think this year they should already have been on the podium. Of course it's possible to fight for the title, but I think it's difficult. But they have to do everything possible, because I think next year is McLaren's last chance."
"I think they have a lot to improve because do you know what? It's not all the fault of the engine. The engine is still not good, but I don't think it's the best chassis in the world.
"So they have to work together, McLaren and Honda, as if they were a single team, and keep Alonso."