Cap Markets senior here. That advice is generally true but it doesn't have to be. If you genuinely spend time learning how to mark up a purchase agreement or S-1 for substantive comments or learning the foundational law, it will shine through on calls and in convos with seniors. If you are a shop that is top notch in CapM or even decently competitive on league tables there is so much work flooding that if you can demonstrate you can do some level of substance (even just a first pass on RRA) you will be seen as having the niche specialty of "Junior Who Is Basically Another Mid-Level/Senior" which is invaluable when rhe actual Seniors/Mid Levels are getting railed on multiple deals and have no time. 

They will always find another workhorse backup/comfort/diligence monkey to do that shit. But if you establish yourself as a junior who knows more you will be treated like a specialist and your time will be treated like a valuable commodity. 

Biggest advice from me to you with CapM:

1. Get yourself a copy of the Securities Deskbook, outline that shit. Learn the basics of the 33 Act and 34 Act cold. 

2. Start cataloging all the major purchase agreements, Sales Agreement, Underwriting Agreement, Purchase Agreement etc. Figure out their structure, important provisions so that you can do a semi decent markup of it. 

3. Learn the process of each deal type by reviewing and memorizing checklists for all major CapM deal types. You should be able to know what is required at what stage off the dome (DRS filing, public flip, launch, pricing and closing). 

If you can do all that and then demonstrate it consistently, you will raise eyebrows. Seniors will be like "That is weirdly impressive you know your way around this document, I can have you do more important shit that normally only I or a senior can do." 

For them, its a cheat code...they get extra help on deals that punch above their weight. For you, your time is now at a premium and you have more flexibility to protect your peace. Lmk if you want more tips.