Potentially beneficial microorganisms have been inoculated into agricultural soils for years. However, concurrent with sequencing advances and successful manipulation of host-associated microbiomes, industry and academia have recently boosted investments into microbial inoculants, convinced they can increase crop yield and reduce fertilizer and pesticide requirements. The efficacy of soil microbial inoculants remains unreliable, and unlike crop breeding, in which target traits (e.g., yield) have long been considered alongside environmental compatibility, microbial inoculant ecology is not sufficiently integrated into microbial selection and production. We propose a holistic temporal model of the shifting constraints on inoculants at five stages of product development and application, and highlight potential conflicts between stages. We question the feasibility of developing ideal soil microbial inoculants with current approaches.