  Resolved dust continuum and CO line ALMA imaging, and in some cases detection
of H$\alpha$ emission, hint that young massive planets are abundant at wide
separations in protoplanetary discs. Here, we show how these observations can
probe the runaway phase of planetary growth in the Core Accretion theory.
Planets in this phase have the right range of masses to account for the
predominantly moderate contrast gaps and rings seen in ALMA observations.
However, we find that these planets gain mass and migrate inward very rapidly.
As a result, the phase when they could produce gaps with properties similar to
those observed is very short, i.e., $t_{\rm gap} \lesssim 0.1$~Myr,
independently of the disc viscosity parameter. This would require many tens to
hundreds of gas giant planets to be born per ALMA system, violating the
available mass budget of solids in realistic discs. This also predicts
preponderance of discs with very wide gaps or complete inner disc holes, which
is not observed. We show that suppression of both planet accretion and
migration by a factor of at least ten is a possible solution to these serious
problems. Future population synthesis models of planet formation should aim to
address both exoplanetary data of older discless planetary systems and ALMA
discs with embedded planets in one framework.
