As a former long-term employee going back to the Level 3 days, the problem with Lumen started when Level 3 acquired TWT, and was accelerated when CTL bought Level 3. The problem is a sales force that is comprised almost entirely of telco dinosaurs who had no interest in their customer's business or any new technologies or processes the company implemented to serve their client base. This went all the way to the top of market sales leadership, where I witnessed this directly.
I watched as sales reps refused to engage in new sales processes because it meant learning something new. I watched sales reps pass up sales because it meant learning how to produce a quote. I watched sales leaders turn a blind eye to unethical conduct at minimum. I consistently listened to managers make excuses for people who refused to do their jobs to avoid rocking the boat.
What Lumen ended up with was a sales force who wanted to sit around and take orders over the phone, with a LEC mentality that was as toxic as it was lazy. If anything involved a sale other than base telco commodities, the majority of sales reps refused to even learn the basics of the technology and expected others to sell and retire quota for them, all the while being encouraged by their leadership. I watched sales reps spend more time looking for holes in the comp plan that they could exploit rather than bothering to demonstrate any interest in their clients.
Lumen is a revolving door of lazy, unmotivated telco retreads who are happy with minimal income, as long as they don't have to do anything. The reps who did care are a very small percentage of the sales force, and most of the good ones would leave. So OF COURSE sales and revenue are down. Clients aren't stupid, and aren't going to give people who belong on a used car lot the time of day when they have actual problems they are looking to solve.
This started in 2016, when Level 3 went from markets with small groups of business professionals to "flooding the market" with anyone with a pulse. It will remain a problem until they flush the lazy, unmotivated telco dinosaurs (including sales leadership) out of the company and focus on quality hires. Once that's done, they can start working with Product Management, who seems to think that telco models for sales, provisioning, and post-sale support of advanced technologies are going to work.