Productivity growth has stagnated over the past decade. This paper argues that the rise of intangible inputs (such as information technology) can cause a slowdown of growth through the effect it has on production and competition. I hypothesize that intangibles create a shift from variable costs to endogenous fixed costs, and use a new measure to show that the share of fixed costs in total costs rises when firms increase ICT and software investments. I then develop a quantitative framework in which intangibles reduce marginal costs and endogenously raise fixed costs, which gives firms with low adoption costs a competitive advantage. This advantage can be used to deter other firms from entering new markets and from developing higher quality products. Paradoxically, the presence of firms with high levels of intangibles can therefore reduce the rate of creative destruction and innovation. I calibrate the model using administrative data on the universe of French firms and find that, after initially boosting productivity, the rise of intangibles causes a 0.6 percentage point decline in long-term productivity growth. The model further predicts a decline in business dynamism, a fall in the labor share and an increase in markups, though markups overstate the increase in firm profits.