Caffeine has a highly subjective efficacy. As shown from recent studies it is highly dependent on genetics.
For further information refer to the following papers:
Astorino, T., Rohmann, R., Firth, K. (2008). Effect of caffeine ingestion on one-repetition maximum muscular strength. European Journal of Applied Physiology. 102 (2), 127-132.
Duncan, M.J., Duncan, M.J., Eyre, E., Grgic, J., Tallis, J. (2019). The effect of acute caffeine ingestion on upper and lower body anaerobic exercise performance. European Journal of Sport Science. 19 (10), 1359-1366.
Southward, K., Rutherfurd-Markwick, K., Badenhorst, C., & Ali, A. (2018). The Role of Genetics in Moderating the Inter-Individual Differences in the Ergogenicity of Caffeine.Nutrients,10(10), 1352. https://doi.org/10.3390/nu10101352 Trexler, E.T., Smith-Ryan, A.E., Roelofs, E.J., Hirsch, K.R., Mock, M.G. (2016). Effects of coffee and caffeine anhydrous on strength and sprint performance. European Journal of Sport Science. 16 (6), 702-P57.