This study presents a comprehensive qualitative synthesis and critical analysis of how foundational mass communication theories have been transformed across the digital media age, spanning the period from 2000 to 2025. Drawing on a systematic integrative review of 23 scholarly manuscripts that collectively engage more than 600 peer-reviewed sources, the investigation examines how ten canonical theories—Agenda Setting, Cultivation, Framing, the Two-Step Flow of Communication, the Spiral of Silence, Uses and Gratifications, Media Dependency, Gatekeeping, Diffusion of Innovation, and Technological Determinism—have evolved, converged, and been reconceptualized in response to the affordances and constraints of digital platforms, algorithmic mediation, and networked communication environments. Employing reflexive thematic analysis grounded in a critical-realist epistemology, the study identifies five overarching meta-themes: (a) the emergence of algorithmic agency as a structural force reshaping every theoretical paradigm; (b) the dialectical tension between expanded user agency and platform-imposed constraint; (c) the increasing platform specificity of communication effects; (d) the convergence and theoretical integration of formerly discrete paradigms; and (e) persistent global inequities in digital communication power structures. The findings indicate that although the core premises of classical theories retain explanatory value, their operative mechanisms, boundary conditions, and societal implications have undergone fundamental transformation. To capture this transformation, the study advances an integrative framework—the Algorithmic Communication Ecology Model (ACEM) that synthesizes insights across all ten theories to account for the recursive, multidirectional, and structurally mediated character of contemporary communication. Significant research gaps are identified, including the scarcity of longitudinal and cross-cultural scholarship, the limited investigation of emergent technologies such as generative artificial intelligence and immersive virtual environments, and the need for methodological innovation that couples computational scales with interpretive depth. The manuscript contributes to communication scholarship by offering a unified analytical lens for understanding how digital transformation has simultaneously preserved, disrupted, and reconstituted the theoretical foundations of the field.