After re-watching the Tony vs Thanos scene again, a thought came to mind and made me wonder. At no point did Doctor Strange ever pause time and simply deal with Thanos and proceed further. This would have obviously been the easy way out. Or at least whilst paused, he could have used the sling ring to cut Thanos' head off. I do note about the many different outcomes that he saw, but I still see this as a possibility.
Simplistic solutions like that would not work. Remember that Thanos already had the Reality Stone when he arrived on Titan.
Some time before the battle with Strange, Thanos had a run in with the Guardians of the Galaxy in which he got stabbed – and killed – by Gamora. To the Guardians' surprise and shock, the scene around them changed and Thanos was whole and intact thanks to the power of the Reality Stone.
Strange probably saw that if he tried any bodily harm that would end Thanos's life in Titan, Thanos would be able to negate it with the Reality Stone. Keeping Thanos in a loop like Strange did with Dormammu would also probably not work - the combined power of the other Stones could probably defeat the Time Stone.
Strange had seen 14,000,605 timelines, and in only one of them the good guys won. I don't know if those 14+ million timelines are all the ones that exist, but they are enough for Doctor Strange to be sure that the final battle against Thanos would not be the one on Titan. The Avengers would only have a chance in a different scenario – my personal opinion is that the battle on Earth was the one with the most favorable outcome because in that context Thanos was practically separated from the stones the whole time – he only manages to use the Power Stone for a brief moment, but that was it.