Pre-built session materials:

Most training programs are pre-written or designed for a "one size fits all" approach. Such programs simply do not fit most teams or businesses that have specific challenges to overcome. Any materials not specific to that group of people is wasted time. This leads to poor engagement and implementation, as well as creating resentment from attendees who undoubtedly have better things to do.
Opaque pricing structures:

Once custom agendas are discussed the costs can increase dramatically, often in confusing ways, making it difficult to justify within an L&D budget. Your choice then become to either keep accepting increasing costs, or you are forced back to "off the shelf" solutions that fit your budget but no longer provide your teams with the efficient, effective training they need.
Poor facilitation:

Many in-person facilitators have learned their craft from watching other inferior facilitators. In turn, they copy the tropes and cliches that have plagued training for decades, such as forced participation, embarrassing role plays, or unnecessary and patronizing "games". These are all things that make attendees dread and resent training as an annoying requirement of their job, rather than the enjoyable gift it should actually be.