Accelerating electrification across transport, industry, and buildings is driving unprecedented growth in electricity demand, placing renewed pressure on power system reliability and operational resilience. At a broad systems level, this demand surge coincides with rapid penetration of variable renewable energy sources, fundamentally altering grid dynamics that were historically optimized for centralized, dispatchable generation. Integrating renewables into modern power systems therefore requires not only capacity expansion, but deep structural transformation of grid architecture, control, and market design. This study frames grid modernization as a critical enabler of reliable, renewable-led electrification. It synthesizes developments in advanced transmission and distribution infrastructure, digital grid technologies, and flexible resource integration. Key mechanisms include advanced forecasting and control enabled by artificial intelligence, grid-scale and distributed energy storage, demand response, power electronics–based inverters, and enhanced interconnection standards. Collectively, these tools address intermittency, congestion, and frequency stability challenges while expanding the system’s ability to absorb high shares of renewable generation. Narrowing to reliability outcomes under accelerating electrification, the analysis emphasizes the role of coordinated planning between generation, networks, and end-use electrification strategies. Electrified loads such as electric vehicles, heat pumps, and industrial electrification can act as flexible assets rather than passive stressors when supported by modernized grids. Evidence from integrated planning and operational frameworks shows that grid modernization reduces curtailment, mitigates peak demand volatility, and enhances resilience against extreme weather and demand shocks. The findings highlight that reliable electrification is not constrained by renewable availability alone, but by the pace of grid modernization. Strategic investment in digitalization, flexibility markets, and regulatory reform is essential to stabilize reliability while scaling renewables, ensuring that rising electricity demand strengthens rather than destabilizes national power systems during the clean energy transition.