What is the most abundant class of enzyme

Why can’t a monomeric receptor tyrosine kinase recruit proteins to the receptor? What would happen if the GTP-ASE protein(GAP) were inhibited?

EDIT: I have found the answer to the the second question posted here. However, I believe I have discovered the answer to the first question, but I fail to understand it. Can someone simplify it into english?

The most abundant class of enzyme linked receptors are receptor tyrosine kinases which respond to signal molecules call for proliferation, differentiation, or survival of different cell types. In response to ligand binding, the receptors oligomerize and the cytosolic tails-which contain tyrosine kinase activity-phosphorylate each other’s tyrosine residues. This autophosphorylation increases the kinases activity of the receptor, and creates binding sites for different proteins. The signaling receptor proteins require phosphotyrosine to bind; hence they do not interact with the inactive monomeric receptor.