Sounds rather like you are doing something right...
However, instead of keeping the AI broke, it may be a better idea to keep the AI afloat. On the lower difficulty levels, where the AI cannot be expected to complete some own research in a reasonable time, I usually don't bother. But on the higher levels (and perhaps Monarch/Large already qualifies for that), I usually keep at least the powerful AIs up to date by gifting them all techs I know, and gifting them surplus luxuries (and sometimes even surplus gpt, if I have any) in the hope that they will research something that I don't know yet, and actually finish it fast enough so that I can trade it from them.
Sometimes it is in vain, but sometimes the AI actually manages to contribute 1-2 techs per era to my research effort, reducing the time I need until launch date.
Usual candidates for this are Sanitation and Communism, which I skip because they are optional (the lost time for researching optionals can usually not be made up again), but which are nevertheless most often useful to have, because a Hospital or Police Station in the right places can significantly increase my commerce, which is required for keeping up the 4-turn research in the later ages.