All you have to do is run into inspiration. It does not matter if it’s your primary or secondary tree. If it’s your primary tree, you get to use glacial to ensure you never miss spells or klepto (which is especially abusive top lane) and farm gold and rng items. Then you can go into a secondary and take whatever you need to top damage off.
Mana champions like Neeko, Ryze, gangplank, pantheon, etc. run into inspiration and are able to click on you endlessly and use this capacity empower their mana pool to outlast your health pool. This is especially frustrating when you consider mana costs are intended weaknesses for some of these champions, and yet they really do not have that weakness. Anyone who complains about going out of mana is a meme, because you have made that impossible for poke champions and this negatively impacts all lanes.
Mana costs do not need to be tuned, access to free mana needs to be removed. In turn, champions with steep mana costs can then have their kits looked at. The reality is that every time you make anything with the capacity to lane in top remotely strong, they can run inspiration and abuse the ever loving shit out of melee characters or characters with less range than themselves. You can welcome Swain and Cass to that crew next patch.
I am of the opinion that the inspiration needs to be changed significantly. Champions should get sustain - both mana and HP - as a means of interaction, not just chugging consumables that come free. Klepto is another abusable keystone that rewards lane bullies for being lane bullies (looking at Kennen). Glacial augment makes Ahri impossible to fuck up on - as if that wasn’t already true before. Does anyone even know what the other ones do? Something about a spellbook - actually that one is cool. The point is, people look at precision and even domination as problematic trees but the reality is that inspiration has been just as abusive but it’s been far more systemic.
Sustain doesn’t need to be gutted, it just needs to be made interactive and inspiration does not do that. Manaflow band is a great example of interaction into sustain, and that’s what inspiration needs to do more of. It should not exist to give lane bullies a pass on their mana costs, nor should it give weak early game champions a pass through their weak early game. If one single tree is granting this, then that tree is a major problem.