If OST went early MGs it hardly could force your mortars off, unless you did push recklessness before that happened.
I suggest you not to use exaggeration+opinions, they both dont mix well. A light vehicle is still reliable since its more mobile than Pgrens, you are just forced to avoid their AT squad only. The rest of the map is yours, adapt, improvise, overcome.
Oswtind last buff turned it into a crutch unit, but it doesnt mean the game is over, it just forces you to go ATG with support or do a steep climb into decent mediums, Shermans or M10 as USF, cromwell as UKF or T34/T70+support.
A replay would help a lot to let other see the weak spot and improve it.
Your point is valid OP, but so is a good suggestion to take gameplay advices. That counts for everyone here posting, no one is game perfect player
I will be more careful writing description. try to separate the personal feeling and situation description.
you did point out some of my weakness, which is great. and give healthy way to improve my skill.